QE 

461 
H84 
1871 
MAIN 


The  Geognosy  of  the  Appalachians  and  the  Origin  of  Crystalline  Rocks, 


ADDRESS 


AMERICAN  ASSOCIATION 


FOR  THE 


ADVANCEMENT    OF    SCIENCE 


THOMAS  STERRY  HUNT,  LL.D. 
n  - 

ON     RETIRING     FK<>M      THE     OFFICE     OF     PRESIDENT    OF     THE      ASXM  IATION. 
INDIANAPOLIS,    AUGUST    16,    1871. 


Printed  in  advance  from  the  Association  Number  of  the  American  Naturalist. 


SALEM: 

NATURALISTS'    AGENCY. 
1871. 


SPECIAL  NOTICE. 


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The  Geognosy  of  the  Appalachians  and  the  Origin  of  Crystalline  Eocks, 


ADDRESS 


TO  THE 


AMERICAN    ASSOCIATION 


FOR  THE 


ADVANCEMENT    OF    SCIENCE, 


BY 


ERRATUM. 


For  foot  notes  on  page  45,  read 


*  Pogg.  Annal.  Ixviii,  319. 

t  Amer.  Jour.  Sci.,  II,  xvi,  218. 


SALEM : 

NATURALISTS'    AGENCY. 
1871. 


SPECIAL  NOTICE. 


We  shall  issue  a 

DOUBLE     NUMBER 

OF  THE 

AMERICAN    NATURALIST, 

to  be  called  the 

A  TTO  1ST     NUMBEK, 


Orders  are  solicited  by  the 

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8  AJL,  IE  M:  ,     IMC  A.  H  H  . 


The  Geognosy  of  the  Appalachians  and  the  Origin  of  Crystalline  Books, 


ADDRESS 


TO  THE 


AMERICAN    ASSOCIATION 


ADVANCEMENT    OF    SCIENCE, 


BY 


THOMAS  STERRY  HUNT,  LL.D. 
M 


ON     RETIRING     FROM    THE    OFFICE    OF    PRESIDENT     OF    THE     ASSOCIATION. 
INDIANAPOLIS,   AUGUST    16,    1871. 


Printed  in  advance  from  the  Association  Number  of  the  American  Naturalist. 


SALEM: 

NATURALISTS'    AGENCY. 
1871. 


SALEM  PRESS, 

Corner  of  Liberty  and  Derby  Streets, 

SALEM,  MASS. 


LOAN   STACK 

GIFT 


ADDRESS 


OF 


THOMAS  STERRY  HUNT, 

ON  RETIRING  FROM 

The  office  of  President  of  the  American  Association  for  the  Advancement  of  Science. 

[Delivered  at  the  20th  meeting  of  the  Association,  at  Indianapolis,  August  16th,  1871.] 

GENTLEMEN  OF  THE  AMERICAN  ASSOCIATION  FOR  THE  ADVANCE- 
MENT OF  SCIENCE  :  — 

IN  coming  before  you  this  evening  my  first  duty  is  to  announce 
the  death  of  Professor  William  Chauvenet.  This  sad  event  was 
not  unexpected,  since,  at  the  time -of  his  election  to  the  presidency 
of  the  Association,  at  the  close  of  our  meeting  at  Salem  in  August, 
1869,  it  was  already  feared  that -failing  health  would  prevent  him 
from  meeting  with  us  at  Troy,  in  1870.  This,  as  you  are  aware, 
was  the  case,  and  I  was  therefore  called  to  preside  over  the  Asso- 
ciation in  his  stead.  In  the  autumn  of  1869,  he  was  compelled  by 
illness  to  resign  his  position  of  Chancellor  of  the  Washington  Uni- 
versity of  St.  Louis,  and  in  December  last  died  at  the  age  of  fifty 
years,  leaving  behind  him  a  record  to  which  science  and  his  countr}- 
may  point  with  just  pride.  During  his  connection  of  fourteen  years 
with  the  Xaval  Academy  at  Annapolis  he  was  the  chief  instrument 
in  building  up  that  institution,  which  he  left  in  1859  to  take  the 
chair  of  Astronomy  and  Mathematics  at  St.  Louis,  where  his  re- 
markable qualities  led  to  his  selection,  in  1862,  for  the  post  of 

(3) 


175 


I  %lf 


4  ADDRESS    OF    T.    STERRY    HUNT. 

chancellor  of  the  university,  which  he  filled  with  great  credit  and 
usefulness  up  to  the  time  of  his  resignation.  *  It  is  not  for  me  to 
pronounce  the  eulogy  of  Professor  Chauvenet,  to  speak  of  his  pro- 
found attainments  in  astronomy  and  mathematics,  or  of  his  pub- 
lished works,  which  have  already  taken  rank  as  classics  in  the 
literature  of  these  sciences.  Others  more  familiar  with  his  field 
of  labor  may  in  proper  time  and  place  attempt  the  task.  All  who 
knew  him  can  however  join  with  me  in  testifying  to  his  excellencies 
as  a  man,  an  instructor  and  a  friend.  In  his  assiduous  devotion 
to  scientific  studies  he  did  not  neglect  the  more  elegant  arts,  but 
was  a  skilful  musician,  and  possessed  of  great  general  culture  and 
refinement  of  taste.  In  his  social  and  moral  relations  he  was 
marked  by  rare  elevation  and  purity  of  character,  and  has  left  to 
the  world  a  standard  of  excellence  in  every  relation  of  life  which 
few  can  hope  to  attain. 

In  accordance  with  our  custom  it  becomes  my  duty  in  quitting 
the  honorable  position  of  president,  which  I  have  filled  for  the 
past  year,  to  address  you  upon  some  theme  which  shall  be  ger- 
mane to  the  objects  of  the  Association.  The  presiding  officer,  as 
you  are  aware,  is  generally  chosen  to  represent  alternately  one  of 
the  two  great  sections  into  which  the  members  of  the  Association 
are  supposed  to  be  divided ;  viz.,  the  students  of  the  natural-his- 
tory sciences  on  the  one  hand,  and  of  the  physico-mathematical 
and  chemical  sciences  on  the  other.  The  arrangement  by  which, 
in  our  organization,  geology  is  classed  with  the  natural-history 
division,  is  based  upon  what  may  fairly  be  challenged  as  a  some- 
what narrow  conception  of  its  scope  and  aims.  While  theoretical 
geology  investigates  the  astronomical,  physical,  chemical  and  bio- 
logical laws  which  have  presided  over  the  development  of  our 
earth,  and  while  practical  geology  or  geognosy  studies  its  natural 
history,  as  exhibited  in  its  physical  structure,  its  mineralogy  and 
its  paleontology,  it  will  be  seen  that  this  comprehensive  science  is 
a  stranger  to  none  of  the  studies  which  are  included  in  the  plan  of 
our  Association,  but  rather  sits  like  a  sovereign,  commanding  in 
turn  the  services  of  all. 

As  a  student  of  geology,  I  scarcely  know  with  which  section  of 
the  Association  I  should  to-day  identify  myself.  Let  me  endeavor 

*  Amer.  Jour.  Sci.,  Ill,  i,  233. 


GEOGNOSY  OF  THE  APPALACHIANS.  0 

rather  to  mediate  between  the  two,  and  show  you  somewhat  of  the 
two-fold  aspect  which  geological  science  presents,  when  viewed 
respectively  from  the  stand-points  of  natural  history  and  of  chem- 
istry. I  can  hardly  do  this  better  than  in  the  discussion  of  a 
subject  which  for  the  last  generation  has  afforded  some  of  the  most 
fascinating  and  perplexing  problems  for  our  geological  students ; 
viz.,  the  history  of  the  great  Appalachian  mountain  chain.  No- 
where else  in  the  world  has  a  mountain  system  of  such  geographi- 
cal extent  and  such  geological  complexity  been  studied  by  such  a 
number  of  zealous  and  learned  investigators,  and  no  other,  it  may 
be  confidently  asserted,  has  furnished  such  vast  and  important 
results  to  geological  science.  The  laws  of  mountain  structure,  as 
revealed  in  the  Appalachians  by  the  labors  o£  the  brothers  Henry 
D.  and  William  B.  Rogers,  of  Lesley  and  of  Hall,  have  given  to 
the  world  the  basis  of  a  correct  system  of  orographic  geology,* 
and  many  of  the  obscure  geological  problems  of  Europe  become 
plain  when  read  in  the  light  of  our  American  experience.  To 
discuss  even  in  the  most  summary  manner  all  of  the  questions 
which  the  theme  suggests,  would  be  a  task  too  long  for  the  present 
occasion,  but  I  shall  endeavor  to-night  in  the  first  place  to  bring 
before  you  certain  facts  in  the  history  of  the  physical  structure, 
the  mineralogy  and  the  paleontology  of  the  Appalachians  ;  and 
in  the  second  place  to  discuss  some  of  the  physical,  chemical  and 
biological  conditions  which  have  presided  over  the  formation  of 
the  ancient  crystalline  rocks  that  make  up  so  large  a  portion  of 
our  great  eastern  mountain  system. 

/.  The  Geognosy  of  the  Appalachian  System. 
The  age  and  geological  relations  of  the  crystalline  stratified  rocks 
of  eastern  North  America  have  for  a  long  time  occupied  the  at- 
tention of  geologists.  A  section  across  northern  New  York,  from 
Ogdensburg  on  the  St.  Lawrence  to  Portland  in  Maine,  shows  the 
existence  of  three  distinct  regions  of  unlike  crystalline  schists. 
These  are  the  Adirondacks  to  the  west  of  Lake  Champlain,  the 
Green  Mountains  of  Vermont,  and  the  White  Mountains  of  New 
Hampshire.  The  lithological  and  mineralogical  differences  between 
the  rocks  of  these  three  regions  are  such  as  to  have  attracted 
the  attention  of  some  of  the  earlier  observers.  Eaton,  one  of  the 

*  Araer.  Jour.  Sci.,  II,  xxx,  406. 


6  ADDRESS    OF   T.    STERRY   HUNT. 

founders  of  American  geology,  at  least  as  early  as  1832,  distin- 
guished in  his  Geological  Text  book  (2d  edition)  between  the  gneiss 
of  the  Adirondacks  and  that  of  the  Green  Mountains.  Adopting 
the  then  received  divisions  of  primary,  transition,  secondary  and 
tertiar}''  rocks,  he  divided  each  of  these  series  into  three  classes, 
which  he  named  carboniferous,  quartzose  and  calcareous  ;  meaning 
by  the  first  schistose  or  argillaceous  strata  such  as,  according  to 
him,  might  include  carbonaceous  matter.  These  three  divisions  in 
fact  corresponded  to  clay,  sand,  and  lime-rocks,  and  were  supposed 
by  him  to  be  repeated  in  the  same  order  in  each  series.  This  was 
apparently  the  first  recognition  of  that  law  of  cycles  in  sedimenta- 
tion upon  which  I  afterwards  insisted  in  1863.*  Without,  so  far  as  I 
am  aware,  defining  tfye  relations  of  the  Adirondacks,  he  referred  to 
the  lowest  or  carboniferous  division  of  the  primary  series,  the  crys- 
talline schists  of  the  Green  Mountains,  while  the  quartzites  and 
marbles  at  their  western  base  were  made  the  quartzose  and  calca- 
reous divisions  of  this  primary  series.  The  argillites  and  sandstones 
lying  still  farther  westward,  but  to  the  east  of  the  Hudson  River, 
were  regarded  as  the  first  and  second  divisions  of  the  transition 
series,  and  were  followed  by  its  calcareous  division,  which  seems  to 
have  included  the  limestones  of  the  Trenton  group ;  all  of  these 
rocks  being  supposed  to  dip  to  the  westward,  and  away  from  the 
central  axis  of  the  Green  Mountains.  Eaton  does  not  appear 
tp  have  studied  the  White  Mountains,  or  to  have  considered  their 
geological  relations.  They  were,  however,  clearly  distinguished 
from  the  former  by  C.  T.  Jackson  in  1844,  when,  in  his  report  on 
the  geology  of  New  Hampshire,  he  described  the  White  Moun- 
tains as  an  axis  of  primary  granite,  gneiss  and  mica-schist,  over- 
laid successively,  both  to  the  east  and  west,  by  what  were  designa- 
ted by  him  Cambrian  and  Silurian  rocks  ;  these  names  having,  since 
the  time  of  Eaton's  publication,  been  introduced  by  English  geol- 
ogists. While  these  overlying  rocks  in  Maine  were  unaltered,  he 
conceived  that  the  corresponding  strata  in  Vermont,  on  the  western 
side  of  the  granitic  axis,  had  been  changed  by  the  action  of  intrusive 
serpentines  and  intrusive  quartzites,  which  had  altered  the  Cam- 
brian into  the  Green  Mountain  gneiss,  and  converted  a  portion  of 
the  fossiliferous  Silurian  limestones  of  the  Champlain  valley  into 
white  marbles,  f  Jackson  did  not  institute  any  comparison  be- 

*  Amer.  Jour.  Sci.,  II,  xxxv,  166. 

t  Geology  of  New  Hampshire,  1GO-162. 


GEOGNOSY  OF  THE  APPALACHIANS.  7 

tween  the  rocks  of  the  White  Mountains  and  those  of  the  Adiron- 
dacks ;  but  the  Messrs.  Rogers  in  the  same  year,  1844,  published 
an  essay  on  the  geological  age  of  the  White  Mountains,  in  which, 
while  endeavoring  to  show  their  Upper  Silurian  age,  they  speak  of 
them  as  having  been  hitherto  regarded  as  consisting  exclusively 
of  various  modifications  of  granitic  and  gneissoid  rocks,  and  as  be- 
longing " to  the  so-called  primary  periods  of  geologic  time."* 
They  however  considered  that  these  rocks  had  rather  the  aspect  of 
altered  paleozoic  strata,  and  suggested  that  they  might  be,  in  part 
at  least,  of  the  age  of  the  Clinton  division  of  the  New  York 
system  ;  a  view  which  was  supported  by  the  presence  of  what  were 
at  the  time  regarded  by  the  Messrs.  Rogers  as  organic  remains. 
Subsequently,  in  1847,|  they  announced  that  they  no  longer  consid- 
ered these  to  be  of  organic  origin,  without  however  retracting 
their  opinion  as  to  the  paleozoic  age  of  the  strata.  Reserving  to 
another  place  in  my  address  the  discussion  of  the  geological  age 
of  the  White  Mountain  rocks,  I  proceed  to  notice  briefly  the  dis- 
tinctive characters  of  the  three  groups  of  crystalline  strata  just 
mentioned,  which  will  be  shown  in  the  sequel  to  have  an  impor- 
tance in  geology  beyond  the  limits  of  the  Appalachians. 

I.  The  Adirondack  or  Laurentide  Series.      The  rocks  of  this 
series,  to  which  the  name  of  the  Laurentian  system  has  been  given, 
may  be   described  as   chiefly  firm  granitic  gneisses,  often  very 
coarse-grained,  and  generally  reddish  or  grayish  in  color.     They 
are  frequently  hornblendic,  but  seldom  or  never  contain  much  mica, 
and  the  mica-schists,  (often  accompanied  with  staurolite,  garnet, 
andalusite  and  cyanite),  so  characteristic  of  the  White  Mountain 
series,  are  wanting  among  the  Laurentian  rocks.     They  are  also 
destitute  of  argillites,  which  are  found   in   the  other  two  series. 
The  quartzites,  and  the  pyroxenic  and  hornblendic  rocks,  asso- 
ciated with  great  formations  of  crystalline  limestone,  with  graph- 
ite, and   immense   beds  of  magnetic  iron  ore,  give   a   peculiar 
character  to  portions  of  the  Laurentian  system. 

II.  The  Grreen  Mountain  Series.     The  quartzo-feldspathic  rocks 
of  this  series  are  to  a  considerable  extent  represented  by  a  fine- 
grained petrosilex  or  eurite,  though  they  often  assume  the  form  of 
a  true  gneiss,  which  is  ordinarily  more  micaceous  than  the  typical 


*  Amer.  Jour.  Sci.,  II,  i,  411. 
tn»id,  II,  v,  116. 


8  ADDRESS    OF    T.    STERRY*  HUNT. 

Laurentian  gneiss.  The  coarse-grained,  porphyritic,  reddish  vari- 
eties common  to  the  latter  are  wanting  in  the  Green  Mountains, 
where  the  gneiss  is  generally  of  pale  greenish  and  grayish  hues. 
Massive  stratified  diorites,  and  epidotic  and  chloritic  rocks,  often 
more  or  less  schistose,  with  steatite,  dark  colored  serpentines  and 
ferriferous  dolomites  and  magnesites  also  characterize  this  gneissic 
series,  and  are  intimately  associated  with  beds  of  iron  ore,  generally 
a  slaty  hematite,  but  occasionally  magnetite.  Chrome,  titanium, 
nickel,  copper,  antimony  and  gold  are  frequently  met  with  in  this  se- 
ries. The  gneisses  often  pass  into  schistose  micaceous  quartzites, 
and  the  argillites,  which  abound,  frequently  assume  a  soft,  unctuous 
character,  which  has  acquired  for  them  the  name  of  talcose  or  na- 
creous slates,  though  analysis  shows  them  not  to  be  magnesian, 
but  to  consist  essentially  of  a  hydrous  micaceous  mineral.  They 
are  sometimes  black  and  graphitic. 

III.  The  White  Mountain  Series.  This  series  is  characterized 
by  the  predominance  of  well  defined  mica- schists  inter  stratified 
with  micaceous  gneisses.  These  latter  are  ordinarily  light  colored 
from  the  presence  of  white  feldspar,  and,  though  generally  fine  in 
texture,  are  sometimes  coarse-grained  and  porphyritic.  They  are 
less  strong  and  coherent  than  the  gneisses  of  the  Laurentian,  and 
pass,  through  the  predominance  of  mica,  into  mica-schists,  which 
are  themselves  more  or  less  tender  and  friable,  and  present  eve^ 
variety,  from  a  coarse  gneiss-like  aggregate  down  to  a  fine-grained 
schist,  which  passes  into  argillite.  The  micaceous  schists  of  this 
series  are  generally  much  richer  in  mica  than  those  of  the  preced- 
ing series,  and  often  contain  a  large  proportion  of  well  defined  crys- 
talline tables  belonging  to  the  species  muscovite.  The  cleavage 
of  these  micaceous  schists  is  generally,  if  not  always,  coincident 
with  the  bedding,  but  the  plates  of  mica  in  the  coarser-grained 
varieties  are  often  arranged  at  various  angles  to  the  cleavage  and 
bedding-plane,  showing  that  they  were  developed  after  sedimenta- 
tion, by  crystallization  in  the  mass  ;  a  circumstance  which  distin- 
guishes them  from  rocks  derived  from  the  ruins  of  these,  which  are 
met  with  in  more  recent  series.  The  White  Mountain  rocks  also 
include  beds  of  micaceous  quartzite.  The  basic  silicates  in  this 
series  are  represented  chiefly  by  dark  colored  gneisses  and  schists, 
in  which  hornblende  takes  the  place  of  mica.  These  pass  occa- 
sionally into  beds  of  dark  hornblende-rock,  sometimes  holding 
garnets.  Beds  of  crystalline  limestone  occasionally  occur  in  the 


GEOGNOSY  OF  THE  APPALACHIANS. 

schists  of  the  White  Mountain  series,  and  are  sometimes  accom- 
panied by  pyroxene,  garnet,  idocrase,  sphene  and  graphite,  as  in 
the  corresponding  rocks  of  the  Laurentian,  which  this  series,  in  its 
more  gneissic  portions,  closely  resembles,  though  apparently  dis- 
tinct geognostically.  The  limestones  are  intimately  associated 
with  the  highly  micaceous  schists  containing  staurolite,  andalusite, 
cyanite  and  garnet.  These  schists  are  sometimes  highly  plumbag- 
inous, as  seen  in  the  graphitic  mica-schist  holding  garnets  in 
Nelson,  New  Hampshire,  and  that  associated  with  cyanite  in  Corn- 
wall, Conn.  To  this  third  series  of  crystalline  schists  belong  the 
concretionary  granitic  veins  abounding  in  beryl,  tourmaline  and 
lepidolite,  and  occasionally  containing  tinstone  and  columbite. 
Granitic  veins  in  the  Laurentian  gneisses  frequently  contain  tour- 
maline, but  have  not,  so  far  as  yet  known,  yielded  the  other  min- 
eral species  just  mentioned.  * 

Keeping  in  mind  the  characteristics  of  these  three  series,  it  will 
be  easy  to  trace  them  southward  by  the  aid  of  the  concise  and  ac- 
curate descriptions  which  Prof.  H.  D.  Rogers  has  given  us  of  the 
rocks  of  Pennsylvania.  In  his  report  on  the  geology  of  this  state 
he  has  distinguished  three  districts  of  various  crystalline  schists, 
which  are  by  him  included  together  under  the  name  of  gneissic 
or  hypozoic  rocks.  Of  these  districts  the  most  northern,  or  the 
South  Mountain  belt,  to  the  northwest  of  the  Mesozoic  basin,  is 
said  to  be  the  continuation  of  the  Highlands  of  New  York  and  New 
Jersey,  which,  crossing  the  Delaware  near  Easton,  is  continued 
southward  through  Pennsylvania  and  Maryland  into  Virginia, 
where  it  appears  in  the  Blue  Ridge.  The  gneiss  of  this  district 
in  Pennsylvania  is  described  as  differing  considerably  from  that  of 
the  southernmost  district,  being  massive  and  granitoid,  often  horn- 
blendic,  with  much  magnetic  iron,  but  destitute  of  any  consider- 
able beds  of  micaceous,  talcose  or  chloritic  slate,  which  mark  the 
rocks  of  the  southern  district.  These  characters  are  sufficient  to 
show  that  the  gneiss  of  this  northern  district  is  lithologically  as 
well  as  geognostically  identical  with  that  of  the  Highlands,  and 
belongs  like  it  to  the  Adirondack  or  Laurentian  system  of  crystal- 
line rocks.  The  gneiss  of  the  middle  district  of  Pennsylvania,  to 
the  south  of  the  Mesozoic,  but  north  of  the  Chester  valley,  is  de- 
scribed by  Rogers  as  resembling  that  of  the  South  Mountain  or 

*Hunt,  Notes  on  Granitic  Rocks;  Amer.  Jour.  Sci.,  Ill,  i,  182. 


10  ADDRESS    OF    T.    STERRY    HUNT. 

northern  district,  and  to  consist  chiefly  of  white  feldspathic  and 
dark  hornblendic  gneiss,  with  very  little  mica,  and  with  crystalline 
limestones. 

The  gneiss  of  the  third  or  southern  district,  that  lying  to  the 
south  of  the  Montgomery  and  Chester  valleys,  comes  from  beneath 
the  Mesozoic  of  New  Jersey  about  six  miles  northeast  of  Trenton, 
and  stretching  southwestward,  occupies  the  southern  border  of 
Pennsylvania,  extending  into  Delaware  and  Maryland.  It  is  sub- 
divided by  Rogers  into  three  belts ;  the  first  or  southernmost 
of  these,  passing  through  Philadelphia,  consists  of  alternations  of 
dark  hornblendic  and  highly  micaceous  gneiss,  with  abundance 
of  mica-slate,  sometimes  coarse-grained,  and  at  other  times  so  fine- 
grained as  to  constitute  a  sort  of  whet-slate.  To  the  northwest- 
ward the  strata  become  still  more  micaceous,  with  garnets  and 
beds  of  hornblende  slate,  till  we  reach  the  second  subdivision, 
which  consists  of  a  great  belt  of  highly  talcose  and  micaceous 
schists,  with  steatite  and  serpentine,  and  is  in  its  turn  succeeded 
by  a  third,  narrow  belt  resembling  the  less  micaceous  members 
of  the  first  or  southernmost  subdivision.  The  micaceous  schists  of 
this  region  abound  in  staurolite,  garnet,  cyanite  and  corundum, 
and  are  traversed  by  numerous  irregular  granitic  veins  containing 
beryl  and  tourmaline.  All  of  these  characters  lead  us  to  refer  the 
gneiss  of  this  southern  district  to  the  third  or  White  Mountain 
series,  with  the  exception  of  the  middle  subdivision,  which  presents 
the  aspect  of  the  second  or  Green  Mountain  series. 

Above  the  hypozoic  gneisses  Rogers  has  placed  his  azoic  or 
semi-metamorphic  series,  which  is  traceable  from  the  vicinity  of 
Trenton  to  the  Schuylkill,  along  the  northern  boundary  of  the 
southern  hypozoic  gneiss  district.  This  series  is  supposed  by 
Rogers  to  be  an  altered  form  of  the  primal  sandstones  and  slates, 
and  is  described  as  consisting  of  a  feldspathic  quartzite  or  eurite, 
containing  in  some  cases  porphyritic  beds  with  crystals  of  feldspar 
and  hornblende,  together  with  various  crystalline  schists ;  includ- 
ing in  fact  the  whole  of  the  great  serpentine  belt  of  Montgomery, 
Chester  and  Lancaster  counties,  with  its  steatites,  hornblendic, 
dioritic,  chloritic,  and  micaceous  schists  (often  garnet-bearing), 
together  with  a  band  of  argillite,  affording  roofing-slates.  With 
this  great  series  are  associated  chrohiic  and  titanic  iron,  and  ores 
of  nickel  and  copper.  Veins  of  albite  with  corundum  also  inter- 
sect this  series  near  Unionville.  We  are  repeatedly  assured  by 


GEOGNOSY  OF  THE  APPALACHIANS.  11 

Rogers  that  these  rocks  so  much  resemble  the  underlying  hypozoic 
gneiss,  as  to  be  readily  confounded  with  them  ;  and  when  compared 
with  the  latter,  as  displayed  in  the  southern  district,  it  is  difficult 
to  believe  that  we  have  in  this  so-called  azoic  or  metamorphic 
series  of  the  Montgomery  and  Chester  valleys,  anything  else  than 
a  repetition  of  these  same  crystalline  schists  which  have  been  de- 
scribed along  their  southern  boundary,  representing  the  Green 
Mountain  and  the  White  Mountain  series.  We  thus  avoid  the  dif- 
ficulty of  supposing  that  we  have  in  this  region  two  sets  of  ser- 
pentinic  rocks,  and  two  of  mica-schists,  lithologically  similar,  but 
of  widely  different  ages,  —  a  conclusion  highly  improbable.  It 
should  be  said  that  Rogers,  in  accordance  with  the  notions  then 
generally  received,  looked  upon  serpentine  as  an  eruptive  rock, 
which  had  altered  the  adjacent  strata,  converting  the  mica-schists 
into  steatitic  and  chloritic  rocks. 

This  so-called  azoic  series,  according  to  Rogers,  underlies  the  au- 
roral limestone  of  Pennsylvania,  thus  apparently  occupying  the 
horizon  of  the  primal  paleozoic  division  or  Potsdam  series.  We 
find,  however,  in  his  report  on  the  geology  of  the  state,  no  satis- 
factory evidence  of  the  identity  of  the  two  series.  On  the  con- 
trary, a  very  different  conclusion  would  seem  to  follow  from  certain 
facts  there  detailed.  The  azoic  or  so-called  metamorphic  primal 
strata  are  said  to  have  a  very  uniform  nearly  vertical  dip,  or  with 
high  angles  to  the  southward,  while  the  micaceous  and  gneissic 
strata  of  the  northern  subdivision  of  the  southern  district  of  so- 
called  hypqzoic  rocks,  limiting  these  last  to  the  south,  present 
either  minute  local  contortions  or  wide  gentle  undulations,  with 
comparatively  moderate  dips,  for  the  most  part  to  the  northward.  * 
From  this,  I  think  we  may  infer  that  the  nearly  vertical  strata  must 
be,  in  truth,  older  underlying  rocks  belonging,  not  to  the  paleozoic 
system,  but  to  our  second  series  of  crystalline  schists.  We  con- 
clude, then,  that  while  the  gneisses  to  the  northwest,  and  probably 
those  along  the  southeast  rim  of  the  Mesozoic  basin  of  Pennsyl- 
vania are  Laurentian,  the  great  valley  southward  to  the  Delaware 
is  occupied  by  the  rocks  of  the  Green  Mountain  and  White  Moun- 
tain series.  The  same  two  types  of  rocks,  extending  to  the  north- 
east, are  developed  about  New  York  city,  in  the  mica-schists  of 
Manhattan  and  the  serpentines  of  Staten  Island  and  Hoboken ; 

*  Rogers,  Geology  of  Pennsylvania,  I,  pp.  69-74,  and  154-158. 


12  ADDRESS    OF    T.    STERRY    HUNT. 

while  in  the  range  of  the  Highlands,  the  gneiss  belt  of  the  South 
Mountain  crosses  the  Hudson  river. 

The  three  series  of  gneissic  rocks  which  we  have  distinguished 
in  our  section  to  the  northward  have,  in  southeastern  New  York, 
as  in  Pennsylvania,  been  grouped  together  in  the  primary  system, 
and  may  thence  all  be  traced  into  western  New  England.  In  Dr. 
Percival's  geological  report  and  map  of  Connecticut,  published  in 
1840,  it  will  be  seen  that  he  refers  to  the  gneiss  of  the  Highlands 
two  gneissic  areas  in  Litchfleld  county ;  the  one  occupying  parts  of 
Cornwall  and  Ellsworth,  and  the  other  extending  from  Torrington, 
northward  through  Winchester,  Norfolk  and  Colebrooke  into  Berk- 
shire county,  Massachusetts.  Farther  investigations  may  confirm 
the  accuracy  of  Percival's  identification,  and  show  the  Laurentian 
age  of  these  New  England  gneisses,  a  view  which  is  apparently  sup- 
ported by  the  mineralogical  characters  of  some  of  the  rocks  in  this 
region.  Emmons  informs  us  that  primary  limestones  with  graphite, 
(perhaps  Laurentian),  are  met  with  in  the  Hoosic  range  in  Massa- 
chusetts east  of  the  Stockbridge  (Taeonic)  limestones. 

The  rocks  of  the  second  series  are  traceable  from  southwestern 
Connecticut  northward  to  the  Green  Mountains  in  Vermont,  and 
the  micaceous  schists  and  gneisses  of  the  third  or  White  Mountain 
series  are  found  both  to  the  east  and  the  west  of  the  Mesozoic  val- 
ley in  Connecticut  and  Massachusetts.  They  also  occupy  a  con- 
siderable area  in  eastern  Vermont,  where  they  are  separated  from 
the  White  Mountain  range  by  an  outcrop  of  rocks  of  the  second 
series.  To  the  southeast  of  the  White  Mountains,  along  our  line  of 
section,  the  same  mica-schists  and  gneisses,  often  with  very  mod- 
erate dips,  extend  as  far  as  Portland,  Maine,  where  they  are  inter- 
rupted by  the  outcropping  of  greenish  chloritic  and  chromiferous 
schists,  in  nearly  vertical  beds,  which  appear  to  belong  to  the  sec- 
ond series. 

I  find  that  the  strata  of  the  second  series  appear  from  beneath 
the  Carboniferous  at  Newport,  Rhode  Island,  in  a  nearly  vertical 
attitude,  and  also  in  the  vicinity  of  Boston  and  Brighton,  Saugus 
and  Lynnfield.  Their  relations  in  this  region  to  the  gneisses  with 
crystalline  limestones  of  Chelmsford,  etc.,  which  I  have  referred  to 
the  Laurentian  series,*  have  yet  to  be  determined. 

We  have  already  mentioned  that  the  crystalline  rocks  of  Penn- 
sylvania pass  into  Maryland  and  Virginia,  where,  as  II.  D.  Rogers 
*  Amer.  Jour.  Sci.,  II,  xlix,  75. 


GEOGNOSY  OF  THE  APPALACHIANS.  13 

informs  us,  they  appear  in  the  mountains  of  the  Blue  Ridge.  It 
remains  to  be  seen  whether  the  three  types  which  we  have  pointed 
out  in  Pennsylvania  are  to  be  recognized  in  this  region.  A  great 
belt  of  crystalline  schists  extends  from  Virginia  through  North 
and  South  Carolina,  and  into  eastern  Tennessee,  where,  according 
to  SarTord,  these  rocks  underlie  the  Potsdam.  It  is  easy,  from  the 
reports  of  Lieber  on  the  geology  of  South  Carolina,  to  identify  in 
this  state  the  two  types  of  the  Green  Mountain  and  White  Moun- 
tain series.  The  former,  as  described  by  him,  consists  of  talcose, 
chloritic  and  epidotic  schists,  with  diorites,  steatites,  actinolite- 
rock  and  serpentines.  It  may  be  noted  that  he  still  adheres  to  the 
notion  of  the  eruptive  origin  of  the  last  three  rocks,  which  the  ob- 
servations of  Emmons,  Logan  and  myself  in  the  Green  Mountains 
have  shown  to  be  untenable.  These  rocks  in  South  Carolina  gen- 
erally clip  at  very  high  angles.  The  great  gneissic  area  of  Anderson 
and  Abbeville  districts  is  described  by  Lieber  a*s  consisting  of  fine- 
grained grey  gneisses  with  micaceous  and  hornblendic  schists,  and 
is  cut  by  numerous  veins  of  pegmatite,  holding  garnet,  tourmaline 
and  beryl.  These  rocks,  which  have  the  characters  of  the  White 
Mountain  series,  appear,  from  the  incidental  observations  to  be 
found  in  Lieber's  reports,  to  belong  to  a  higher  group  than  the 
chloritic  and  serpentinic  series,  and  to  dip  at  comparatively  mod- 
erate angles. 

Professor  Emmons,  whose  attention  was  early  turned  to  the  ge- 
ology of  western  New  England,  did  not  distinguish  between  the 
three  tj'pes  which  we  have  defined,  but,  like  Rogers  in  Pennsylva- 
nia, included  all  the  crystalline  rocks  of  that  region  in  the  primary 
system.  It  is  to  him,  however,  that  we  owe  the  first  correct  no- 
tions of  the  geological  nature  and  relations  of  the  Green  Mountains. 
These,  he  has  remarked,  are  often  made  to  include  two  ranges  of 
hills  belonging  to  different  geological  series.  The  eastern  range, 
including  the  Hoosic  Mountain  in  Massachusetts,  and  Mount 
Mansfield  in  Vermont,  he  referred  to  the  primary ;  which  he  de- 
scribed as  including  gneiss,  mica-schist,  talcose  slate  and  horn- 
blende, with  beds  and  veins  of  granite,  limestone,  serpentine  and 
trap.  He  declared,  moreover,  that  there  is  no  clear  line  of  de- 
marcation among  the  various  schistose  primary  rocks,  and  cited, 
as  an  illustration,  the  passage  into  each  other  of  serpentine,  stea- 
tite and  talcose  schist.  His  description  of  the  crystalline  rocks  of 
this  range  will  be  recognized  as  comprehensive  and  truthful. 


14  ADDRESS    OF    T.    STERRY    HUNT. 

To  the  west  of  the  hills  of  primary  schist,  he  placed  his  Taconic 
system,  named  from  the  Taconic  hills,  which  run  from  north  to 
south  along  the  boundary  line  of  New  York  and  Massachusetts  and 
form  a  range  parallel  with  the  Green  Mountains.  The  lower  por- 
tions of  the  Taconic  system,  according  to  Emmons,  are  schistose 
rocks  made  up  from  the  ruins  of  the  primary  schists  which  lie  to 
the  east  of  them.  Thus  the  talcose  schists  of  Berkshire  are  said 
to  be  regenerated  rocks,  belonging  to  the  newer  system,  but  show- 
ing the  color  and  texture  of  the  older  talcose  schists  from  which 
they  were  formed.  How  far  this  is  true  of  these  particular  strata 
may  be  a  question,  for  there  is  reason  to  believe  that  Emmons 
included  among  his  Taconic  rocks  some  beds  belonging  to  the  older 
crystalline  series  of  the  Green  Mountains  ;  yet  it  is  not  less  true  that 
the  possibility  of  derived  rocks  of  this  kind  is  one  which  has  been 
too  much  overlooked  by  geologists.  Emmons  elsewhere  remarks 
that  while  the  talcose  slates  of  the  primary  are  associated  with 
steatite  and  with  hornblende,  these  are  never  found  in  the  Taconic 
rocks,  and  also,  that  epidote,  actinolite,  titanium  (rutile),  etc., 
which  are  characteristic  minerals  of  the  primary,  are  wanting  in 
the  Taconic  system. 

The  statements  of  Emmons  on  this  point,  were  sufficiently  ex- 
plicit ;  he  included  in  the  primary  system  all  of  the  crystalline 
schists  of  the  Green  Mountains,  except  certain  talcose  and  mi- 
caceous beds,  which  he  supposed  to  be  composed  from  the  ruins 
of  similar  strata  in  the  primary,  and  to  constitute,  with  a  great 
mass  of  other  rocks,  the  Taconic  system  ;  which  was,  in  its  turn, 
unconformably  overlaid  by  the  Potsdam  sandstone  and  Calciferous 
sandrock  of  the  New  York  system.  His  views  have,  however,  been 
misunderstood  by  more  than  one  of  his  critics  ;  thus,  Mr.  Marcou, 
while  defending  the  Taconic  system,  makes  it  to  include  the  three 
groups  just  mentioned,  viz. :  I,  the  Green  Mountain  gneiss  ;  II,  the 
Taconic  strata  as  defined  by  Emmons,  and  III,  the  Potsdam  sand- 
stone,* thus  uniting  in  one  system  the  crystalline  schists  and  the 
overlying  uncrystalline  fossiliferous  sediments,  in  direct  opposition 
to  the  plainly  expressed  teachings  of  Emmons,  as  laid  down  in  his 
report  on  the  Geology  of  the  Northern  District  of  New  York,  and 
later,  in  1846,  f  in  his  work  on  the  Taconic  system. 

In  the  geological  survey  of  the  state  of  New  York,  the  rocks  of 

*  Proc.  Bost.  Nat.  Hist.  Soc.,  Nov.  6, 18(51,  and  Amer.  Jour.  Sci.,  II,  xxxiii,  282. 
t  Loc.  cit.,  p.  139,  and  Agricult.,  N.  York,  I,  53. 


GEOGNOSY  OF  THE  APPALACHIANS.  15 

the  Champlain  division,  including  the  strata  from  the  base  of  the 
Potsdam  sandstone  to  the  summit  of  the  Loraine  or  Hudson  River 
shales,  had,  by  his  colleagues,  been  looked  upon  as  the  lowest  of 
the  paleozoic  system.  Professor  Emmons,  however,  was  led  to 
regard  the  very  dissimilar  strata  of  the  Taconic  hills  as  constituting 
a  distinct  and  more  ancient  series.  A  similar  view  had  been  held  by 
Eaton,  who  placed,  as  we  have  already  seen,  above  the  crystalline 
schists  of  the  Green  Mountains,  his  primary  quartzose  and  calcare- 
ous formations,  followed  to  the  westward  by  transition  argillites  and 
sandstones,  which  latter  appear  to  have  corresponded  to  the  Pots- 
dam sandstone  of  New  York.  Emmons,  however,  gave  a  greater 
form  and  consistency  to  this  view,  and  endeavored  to  sustain  it  by 
the  evidence  of  fossils,  as  well  as  by  structure.  The  Taconic  sys- 
tem, as  defined  by  him,  may  be  briefly  described  as  a  series  of 
uncrystalline  fossiliferous  sediments  reposing  unconformably  on 
the  crystalline  schists  of  the  Green  Mountains,  and  partly  made 
up  of  their  ruins ;  while  it  is,  at  the  same  time,  overlaid  uncon- 
formably by  the  Potsdam  and  Calciferous  formations  of  the  Cham- 
plain  division,  and  constitutes  the  true  base  of  the  paleozoic 
column, — thus  occupying  the  position  of  the  British  Cambrian. 

Although  he  claimed  to  have  traced  this  Taconic  system  through- 
out the  Appalachian  chain  from  Maine  to  North  Carolina,  it  is 
along  the  confines  of  Massachusetts  and  New  York  that  its  devel- 
opment was  most  minutely  studied.  He  divided  it  into  a  lower 
and  an  upper  division,  and  estimated  its  total  thickness  at  not  less 
than  thirty  thousand  feet,  consisting,  in  the  order  of  deposition, 
of  the  following  members  :  —  1.  Granular  quartz  ;  2.  Stockbridge 
limestone  ;  3.  Magnesian  slate  ;  4.  Sparry  limestone  ;  5.  Roofing- 
slate,  graptolitic  ;  6.  Silicious  conglomerate ;  7.  Taconic  slate  ;  8. 
Black  slate.  The  apparent  order  of  superposition  differs  from  this, 
and  it  was  conceived  by  Professor  Emmons  that  during  the  accu- 
mulation of  these  Taconic  rocks,  the  Green  Mountain  gneiss,  which 
formed  the  eastern  border  of  the  basin,  was  gradually  elevated  so 
as  to  bring  successively  the  older  members  above  the  ocean  from 
which  the  sediments  were  being  deposited.  From  this  it  resulted 
that  the  upper  members  of  the  system,  such  as  the  black  slates, 
were  confined  to  a  very  narrow  belt,  and  never  extended  far  east- 
ward ;  although  he  admits  that  denudation  may  have  removed  large 
portions  of  these  upper  beds.  At  a  subsequent  period,  a  series  of 
parallel  faults,  with  upthrows  on  the  eastern  side,  is  supposed  to 


16  ADDRESS    OP    T.    STERRY    HUNT. 

have  broken  the  strata,  given  them  an  eastward  dip,  and  caused  the 
newer  beds  to  pass  successively  beneath  the  older  ones,  thus  pro- 
ducing an  apparently  inverted  succession,  and  making  their  present 
seeming  order  of  superposition  completely  deceptive.  In  speaking 
of  this  supposed  arrangement  of  the  members  of  his  Taconic  sys- 
tem, Emmons  alluded  to  them  as  "  inverted  strata  ;"  while  by  Mr. 
Marcou,  the  strata  were  said  to  be  "overturned  on  each  side  of  the 
crystalline  and  eruptive  rocks  which  occupy  the  centre  of  the  chain, 
producing  thus  a  fan-shaped  structure,"  etc.*  I  have  elsewhere 
shown  that  this  notion,  though  to  some  extent  countenanced  by 
his  vague  and  inaccurate  use  of  terms,  was  never  entertained 
by  Emmons,  whose  own  view,  as  defined  in  his  Taconic  System  (p. 
17),|  is  that  just  explained. 

The  view  of  Emmons  that  there  exists  at  the  western  base  of 
the  Green  Mountains,  older  fossiliferous  series  underlying  the 
Potsdam,  met  with  general  opposition  from  American  geologists. 
In  May,  1844,  H.  D.  Rogers,  in  his  address  as  President,  before  the 
American  Association  of  Geologists,  then  met  at  Washington,  crit- 
icised this  view  at  length,  and  referred  to  a  section  from  Stock- 
bridge,  Massachusetts,  to  the  Hudson  River,  made  by  W.  B.  Rogers 
and  himself,  and  by  them  laid  before  the  American  Philosophical 
Society  in  January,  1841.  They  then  maintained  that  the  quartz- 
rock  of  the  Hoosic  range  was  Potsdam,  the  Berkshire  marble  iden- 
tical with  the  blue  limestone  of  the  Hudson  valley,  and  the  asso- 
ciated micaceous  and  talcose  schists,  altered  strata  of  the  age  of  the 
slates  at  the  base  of  the  Appalachian  system ;  that  is  to  say,  pri- 
mal in  the  nomenclature  of  the  Pennsylvania  survey. 

In  1843  Mather  had  asserted  the  Champlain  age  of  the  same 
crystalline  rocks,  and  claimed  that  the  whole  of  the  division  was 
there  represented,  including  the  Potsdam,  the  Hudson  River  group, 
and  the  intermediate  limestones.  |  The  conclusion  of  Mather  was 
cited  with  approbation  by  Rogers,  who  apparently  adopted  it,  and 

*  Comptes  Rendus  de  1'Acad.,  LIII,  804. 

fSee  my  farther  discussion  of  the  matter,  Amer.  Jour.  Sci.,  II,  xxxii,  427,  xxxiii, 
135,  281.  It  is  by  an  oversight  that  I  have,  in  the  latter  volume,  page  136,  represented 
Barrande  as  sharing  the  misconception  of  Marcou,  although  his  language,  without 
careful  scrutiny,  would  lead  us  to  such  a  conclusion.  In  fact  in  the  Bull.  Soc.  Geol.  de 
France  (II,  xviii,  231),  in  an  elaborate  study  of  the  Taconic  question,  Barrande  heads 
a  section  thus,  "  Renversement  conqu  pour  tout  un  systeme,"  and  then  proceeds  to  show 
that  the  renversement  or  overturn  is  only  apparent,  by  explaining,  in  the  language  of 
Emmons,  the  view  already  set  forth  above. 

J  Geology  of  the  Southern  District  of  New  York,  p.  438. 


GEOGNOSY  OF  THE  APPALACHIANS.  17 

claimed  that  Hitchcock  held  a  similar  view.  It  will  be  seen  that 
these  geologists  thus  united  in  one  group,  the  schists  of  the  Hoosic 
range  (regarded  by  Emmons  as  primary),  with  those  of  the  Ta- 
conic  range,  and  referred  both  to  the  age  of  the  Champlain  divis- 
ion, the  whole  of  which  was  supposed  to  be  included  in  the  group. 
In  the  same  address  Professor  Rogers  raised  a  very  important 
question.  Having  referred  to  the  Potsdam  sandstone,  which  on 
Lake  Champlain  forms  the  base  of  the  paleozoic  system,  he  in- 
quires, "Is  this  formation  then  the  lowest  limit  of  our  Appalachian 
masses  generally,  or  is  the  system  expanded  downward  in  other 
districts  by  the  introduction  beneath  it  of  other  conformable  sed- 
imentary rocks  ?"  He  then  proceeded  to  state  that  from  the  Sus- 
quehanna  River,  southwestward,  a  more  complex  series  appears  at 
the  base  of  the  lower  limestone  than  to  the  north  of  the  Schuylkill, 
and  in  some  parts  of  the  Blue  Ridge  he  includes  in  the  primal  di- 
vision (beneath  the  Calciferous  sandrock)  "  at  least  four  indepen- 
dent and  often  very  thick  deposits,  constituting  one  general  group, 
in  which  the  Potsdam  or  white  sandstone  (with  Scolithus)  is  the 
second  in  descending  order."  This  sandstone  is  overlaid  by  many 
hundred  feet  of  arenaceous  and  ferriferous  fucoidal  slate,  and  un- 
derlaid by  coarse  sandy  shales  and  flagstones ;  below  which,  in 
Virginia  and  East  Tennessee,  is  a  series  of  heterogeneous  con- 
glomerates, which  rest  on  a  great  mass  of  crystalline  strata.  The 
accuracy  of  these  statements  is  confirmed  by  Safford,  who,  in  his 
recent  report  on  the  geology  of  Tennessee  (1869),  places  at  the 
base  of  the  column  a  great  series  of  crystalline  schists,  apparently 
representatives  of  those  of  southeastern  Pennsylvania.  Upon 
these  repose  what  Safford  designates  as  the  Potsdam  group,  in- 
cluding, in  ascending  order,  the  Ococee  slates  and  conglomerates, 
estimated  at  10,000  feet,  and  the  Chilhowee  shales  and  sandstones, 
2,000  feet  or  more,  with  fucoids,  worm-burrows  and  Scolithus. 
These  are  conformably  overlaid  by  the  Knoxville  division,  con- 
sisting of  fucoidal  sandstones,  shales,  and  limestones,  the  latter 
two  holding  fossils  of  the  age  of  the  Calciferous  sandrock.  It  is 
noteworthy  that  these  rocks  are  greatly  disturbed  by  faults,  and 
that  in  Chilhowee  Mountain  the  lower  conglomerates  are  brought 
on  the  east  against  the  Carboniferous  limestone,  by  a  vertical  dis- 
placement of  at  least  12,000  feet.  The  general  dip  of  all  these 
'  strata,  including  the  basal  crystalline  schists,  is  to  the  southeast. 
The  primal  paleozoic  rocks  of  the  Blue  Ridge  were  then  by  Rog- 

AMER.    NAT.,    ASSOC.    NUMBER.  2 


18  ADDRESS    OF   T.    STERRY   HUNT. 

ers,  as  now  by  Safford,  looked  upon  as  wholly  of  Potsdam  age,  in 
eluding  the  Scolithus  sandstone  as  a  subordinate  member,  so  that 
the  strata  beneath  this  were  still  regarded  as  belonging  to  the  New 
York  system.  Hence,  while  Rogers  inquires  whether  the  Taconic 
system  "may  not  along  the  western  border  of  Vermont  and  Mas- 
sachusetts include  also  some  of  the  sandy  and  slaty  strata  here 
spoken  of  as  lying  beneath  the  Potsdam  sandstone"*  he  would  still 
embrace  these  lower  strata  in  the  Champlain  division. 

Thus  we  see  that  at  an  early  period  the  rocks  of  the  Taconic 
system  were,  by  Rogers  and  Mather,  referred  to  the  Champlain  divi- 
sion of  the  New  York  system,  a  conclusion  which  has  been  sus- 
tained by  subsequent  observations.  Before  discussing  these,  and 
their  somewhat  involved  history,  we  may  state  two  questions  which 
present  themselves  in  connection  with  this  solution  of  the  problem. 
First,  whether  the  Taconic  system,  as  defined  by  Emmons,  includes 
the  whole  or  a  part  of  the  Champlain  division ;  and  second,  wheth- 
er it  embraces  any  strata  older  or  newer  than  the  members  of  this 
portion  of  the  New  York  system.  With  reference  to  the  first 
question  it  is  to  be  remarked  that  in  their  attempts  to  compare  the 
Taconic  rocks  with  those  of  the  Champlain  division  as  seen  farther 
to  the  west,  observers  were  led  by  lithological  similarities  to  iden- 
tify the  upper  members  of  the  latter  with  certain  portions  of  the 
Taconic.  In  fact,  the  Trenton  limestone,  with  the  Utica  slates 
and  the  Loraine  or  Hudson  River  shales,  making  together  the  upper 
half  of  the  Champlain  division  (in  which  Emmons  moreover  in- 
cluded the  overlying  Oneida  and  Medina  conglomerates  and  sand- 
stones) ,  have  in  New  York  an  aggregate  thickness  of  not  less  than 
three  or  four  thousand  feet,  and  offer  many  lithological  resem- 
blances to  the  great  mass  of  sediments  at  the  western  base  of  the 
Green  Mountains,  to  which  the  name  of  Taconic  had  been  applied. 
It  is  curious  to  find  that  Emmons,  in  1842,  referred  to  the  Medina 
the  Red  sandrock  of  the  east  shore  of  Lake  Champlain,  since  shown 
to  be  Potsdam  ;  and,  moreover,  placed  the  Sillery  sandstone  of  the 
neighborhood  of  Quebec  at  the  summit  of  the  Champlain  division, 
as  the  representative  of  the  Oneida  conglomerate ;  while  at  the 
same  time  he  noticed  the  great  resemblance  which  this  sandstone, 
with  its  adjacent  limestones,  bore  to  similar  rocks  on  the  confines 

of  Massachusetts,  already  referred  by  him  to  the  Taconic  system,  t 

• 

*  Amer.  Jour.  Sci.,  I,  xlvii,  152, 153. 

fGeol.  Northern  District  of  New  York,  pp.  124, 125. 


GEOGNOSY  OF  THE  APPALACHIANS.  19 

This  view  of  Emmons  as  to  the  Quebec  rocks  was  adopted  by 
Sir  William  Logan,  when,  a  few  years  afterwards,  he  began  to 
study  the  geology  of  that  region.  The  sandstone  of  Sillery  was 
described  by  him  as  corresponding  to  the  Oneida  or  Shawangunk 
conglomerate,  while  the  limestones  and  shales  of  the  vicinity, 
which  were  supposed  to  underlie  it,  were  regarded  as  the  repre- 
sentatives of  the  Trenton,.  Utica,  and  Hudson  River  formations.  * 
By  following  these  rocks  along  the  western  base  of  the  Appalach- 
ians into  Vermont  and  Massachusetts,  they  were  found  to  be  a 
continuation  of  the  Taconic  system,  which  Sir  William  was  thus 
led  to  refer  to  the  upper  half  of  the  Champlain  division,  as  had 
already  been  done  by  Professor  Adams  in  1847.f  As  regards  the 
crystalline  strata  of  the  Appalachians  in  this  region,  he,  however, 
rejected  the  view  of  Emmons,  and  maintained  that  put  forward  by 
the  Messrs.  Rogers  in  1841,  viz.,  that  these,  instead  of  being  older 
rocks,  were  but  these  same  upper  formations  of  the  Champlain 
division  in  an  altered  condition  ;  a  view  which  was  maintained  dur- 
ing several  years  in  all  of  the  publications  of  those  connected  with 
the  geological  survey  of  Canada. 

This  conclusion,  so  far  as  regards  the  age  of  the  unaltered  fos- 
siliferous  rocks  from  Quebec  to  Massachusetts,  was  supposed  to 
be  confirmed  by  the  evidence  of  organic  remains  found  in  them  in 
Vermont.  Mr.  Emmons  had  described  as  characteristic  of  the 
upper  part  of  the  Taconic  system,  two  crustaceans,  to  which  he 
gave  the  names  of  Atops  trilineatus  and  Elliptoceplialus  asaphoides  ; 
the  other  fossils  noticed  by  him  being  graptolites,  fucoids,  and  what 
were  apparently  the  marks  of  annelids.  In  1847  Professor  James 
Hall,  in  the  first  volume  of  his  Paleontology,  declared  the  Atops  of 
Emmons  to  be  identical  with  Triarthrus  (Catymene)  Beckii,  a  char- 
acteristic fossil  of  the  Utica  slate ;  while  the  Elliptocephalus  was 
referred  by  him  to  the  genus  Olenus,  now  known  to  belong  to  the 
primordial  fauna  of  Sweden,  where  it  is  found  in  slates  lying  be- 
neath the  orthoceratite  limestone,  and  near  the  base  of  the  paleo- 
zoic series.  Although,  as  it  now  appears,  the  geological  horizon  of 
the  Olenus  slates  was  well  known  to  Hisinger,  this  author  in  his 
classic  work,  Lethcea  Suecica,  published  in  1837,  represents,  by 
some  unexplained  error,  these  slates  as  overlying  the  orthoceratite 


*Geol.  Survey  of  Canada,  1847-48,  pp.  27,  57;  and  Amer.  Jour.  Sci.,  H,  ix,  12. 
f  Amer.  Jour.  Sci.,  II,  v,  108. 


20  ADDRESS    OF   T.    STERRY   HUNT. 

limestone,  which  is  the  equivalent  of  the  Trenton  limestone  of  the 
Champlain  division.  Hence,  as  Mr.  Barrande  has  remarked,  Hall 
was  justified  by  the  authority  of  Hisinger's  published  work  in  as- 
signing to  the  Olenus  slates  of  Yermont  a  position  above  that  lime- 
stone, and  in  placing  them,  as  he  then  did,  on  the  horizon  of  the 
Hudson  River  or  Loraine  shales.  The  double  evidence  afforded  by 
these  two  fossil  forms  in  the  rocks  of  Vermont,  served  to  confirm 
Sir  William  Logan  in  placing  in  the  upper  part  of  the  Champlain 
division  the  rocks  which  he  regarded  as  their  stratigraphical  equiv- 
alents near  Quebec ;  and  which,  as  we  have  seen,  had  some  years 
before  been  by  Emmons  himself  assigned  to  the  same  horizon. 
The  remarkable  compound  graptolites  which  occur  in  the  shales 
of  Pointe  Levis,  opposite  Quebec,  were  described  by  Professor 
James  Hall  in  the  report  of  the  Geological  Survey  of  Canada  for 
1857,  and  were  then  referred  to  the  Hudson  River  group  ;  nor  was 
it  until  August,  1860,  that  Mr.  Billings  described  from  the  lime- 
stones of  this  same  series  at  Pointe  Levis  a  number  of  trilobites, 
among  which  were  several  species  of  Agnostus,  Dikelocephalus, 
Bathyurus,  etc.,  constituting  a  fauna  whose  geological  horizon  he 
decided  to  be  in  the  lower  part  of  the  Champlain  division. 

Just  previous  to  this  time,  in  the  Report  of  the  Regents  of  the 
University  of  New  York  for  1859,  Professor  Hall  had  described  and 
figured  by  the  name  of  Olenus,  two  species  of  trilobites  from  the 
slates  of  Georgia,  Vermont,  which  Emmons  had  wrongly  referred 
to  the  genus  Paradoxides.  They  were  at  once  recognized  by  Bar- 
rande, who  called  attention  to  their  primordial  character,  and  thus 
led  to  a  knowledge  of  their  true  stratigraphical  horizon,  and  to  the 
detection  of  the  singular  error  in  Hisinger's  book,  already  noticed, 
by  which  American  geologists  had  been  misled.*  They  have 
since  been  separated  from  Olenus,  and  by  Professor  Hall  referred 
to  a  new  and  closely  related  genus,  which  he  has  named  Olenellus, 
and  which  is  now  regarded  as  belonging  to  the  horizon  of  the  Pots- 
dam sandstone,  to  which  we  shall  presently  advert. 

Farther  studies  of  the  fossiliferous  rocks  near  Quebec  showed 
the  existence  of  a»  mass  of  sediments  estimated  at  about  1200 
feet,  holding  a  numerous  fauna,  and  corresponding  to  a  great 
development  of  strata  about  the  age  of  the  Calciferous  and  Chazy 
formations,  or  more  exactly  to  a  formation  occupying  a  position 

*For  the  correspondence  on  this  matter  between  Barrande,  Logan  and  Hall,  see 
Amer.  Jour.  Sci.,  II,  xxxi,  210-226. 


GEOGNOSY  OF  THE  APPALACHIANS.  21 

between  these  two,  and  constituting,  as  it  were,  beds  of  passage 
between  them.  In  this  new  formation  were  included  the  grapto- 
lites  already  described  by  Hall,  and  the  numerous  Crustacea  and 
brachiopoda  described  by  Billings,  all  of  which  belong  to  the  Levis 
slates  and  limestones.  To  these  and  their  associated  rocks  Sir 
William  Logan  then  gave  the  name  of  the  Quebec  group,  including, 
besides  the  fossiliferous  Levis  formation,  a  great  mass  of  overlying 
slates,  sandstones  and  magnesian  limestones,  hitherto  without  fos- 
sils, which  have  been  named  the  Lauzon  rocks,  and  the  Sillery 
sandstones  and  shales,  which  he  supposed  to  form  the  summit  of 
the  group,  and  which  had  afforded  only  an  Obolella  and  two  species 
of  Lingula ;  *  the  volume  of  the  whole  group  being  about  7000  feet. 

The  paleontological  evidence  thus  obtained  by  Billings  and  by 
Hall,  both  from  near  Quebec  and  in  Vermont,  led  to  the  conclusion 
that  the  strata  of  these  regions,  so  much  resembling  the  upper 
members  of  the  Champlain  division,  were  really  a  great  develop-- 
ment,  in  a  modified  form,  of  some  of  its  lower  portions.  Their 
apparent  stratigraphical  relations  were  explained  by  Logan  by  the 
supposition  of  "an  overturned  anticlinal  fold,  with  a  crack  and  a 
great  dislocation  running  along  the  summit,  by  which  the  Quebec 
group  is  brought  to  overlie  the  Hudson  Kiver  group.  Sometimes 
it  may  overlie  the  overturned  Utica  formation,  and  in  Vermont 
points  of  the  overturned  Trenton  appear  occasionally  to  emerge 
from  beneath  the  overlap."  He,  at  the  same  time,  declared  that 
"from  the  pl^sical  structure  alone,  no  person  would  suspect  the 
break  that  must  exist  in  the  neighborhood  of  Quebec,  and,  without 
the  evidence  of  fossils,  every  one  would  be  authorized  to  deny  it."| 

The  rocks  from  western  Vermont,  which  had  furnished  to  Hall 
the  species  of  Olenellus,  have  long  been  known  as  the  Red  sand- 
rock,  and  as  we  have  seen,  were  by  Emmons,  in  1842,  referred  to 
the  age  of  the  Medina  sandstone,  a  view  which  the  late  Professor 
Adams  still  maintained  as  late  as  1847.  j  In  the  mean  time 
Emmons  had,  in  1855,  declared  this  rock  to  represent  the  Cal- 
ciferous  and  Potsdam  formations,  the  brown  sandstones  of  Bur- 
lington and  Charlotte,  Vermont,  being  referred  to  the  latter.  § 


*See  Billings,  Paleozoic  Fossils  of  Canada,  p.  69. 

t  Logan's  letter  to  Barrande,  Amer.  Jour.  Sci.,  II,  xxxi,  218.    The  true  date  of  this 
letter  was  December  31st,  1860.  but,  by  a  misprint,  it  is  made  1831. 
t  Adams,  Amer.  Jour.  Sci.,  H,  v,  108. 
§  Emmons,  American  Geology,  II,  128. 


22  ADDRESS    OF   T.    STERRY   HUNT. 

This  conclusion  was  confirmed  by  Billings,  who,  in  1861,  after  vis- 
iting the  region  and  examining  the  organic  remains  of  the  Red 
sandrock,  assigned  to  it  a  position  near  the  horizon  of  the  Pots- 
dam.* Certain  trilobites  found  in  this  Red  sandrock  by  Adams 
in  1847,  were  by  Hall  recognized  as  belonging  to  the  European 
genus  Conocephalus  (=  Conocephalites  and  Conocoryphe) ,  whose 
geological  horizon  was  then  undetermined.!  Tne  formation  in 
question  consists  in  great  part  of  a  red  or  mottled  granular  dolo- 
mite, associated  with  beds  of  fucoidal  sandstone,  conglomerates 
and  slates.  These  rocks  were  carefully  examined  by  Logan  in 
Swanton,  Vermont,  where,  according  to  him,  they  have  a  thick- 
ness of  2200  feet,  and  include  toward  their  base  a  mass  of  dark 
colored  shales  holding  Olenellus  with  Conocephalites,  Obolella, 
etc. ;  Conocephalites  Teucer,  Billings,  being  common  to  the  shales 
and  the  red  sandy  beds. J  Many  of  these  fossils  are  also  found  at 
Troy  and  at  Bald  Mountain,  New  York,  where  they  accompany 
the  Atops  of  Emmons,  now  recognized  by  Billings  as  a  species  of 
Conocephalites. 

A  similar  condition  of  things  extends  northeastward  along  the 
Appalachian  region.  On  the  south  side  of  the  St.  Lawrence  below 
Quebec  a  great  thickness  of  limestones,  sandstones,  and  slates, 
formerly  referred  to  the  Quebec  group,  is  now  regarded  by  Billings 
as,  in  part  at  least,  of  the  Potsdam  formation  ;  while  on  the  coast 
of  Labrador,  and  in  northern  Newfoundland  the  same  formation, 
characterized  by  the  same  fossils  as  in  Vermont,  is  largely  devel- 
oped, attaining  in  some  parts,  according  to  Murray,  a  thickness  of 
3000  feet  or  more.  Along  the  northern  coast  of  the  island  it  is 
nearly  horizontal,  and  appears  to  be  conformably  overlaid  by  about 
4000  feet  of  fossiliferous  strata  representing  the  Calclferous  sand- 
rock  and  the  succeeding  Levis  formation. 

Mr.  Billings  has  described  a  section  from  the  Laurentian  of 
Crown  Point,  New  York,  to  Cornwall,  Vermont,  from  which  it  ap- 
pears that  to  the  eastward  of  a  dislocation  which  brings  up  the 
Potsdam  to  overlie  the  higher  members  of  the  Champlain  division, 
the  Potsdam  is  itself  overlaid,  at  a  small  angle,  by  a  great  mass  of 
limestones  representing  the  Calciferous,  and  having  at  the  summit 
some  of  the  characteristic  fossils  of  the  Levis  formation.  Next  in 

*  Amer.  Jour.  Sci.,  II,  xxxii,  232. 

flbid.,  II,  xxxiii,  374. 

J  Geology  of  Canada,  1863,  p.  281.    Amer.  Jour.  Sci.,  II,  xlvi,  224. 


GEOGNOSY  OF  THE  APPALACHIANS.  23 

ascending  order  are  not  less  than  2000  feet  of  limestones  with 
Trenton  fossils  (embracing  probably  the  Chazy  division),  while  to 
the  east  of  this  the  Levis  again  appears,  including  the  white  Stock- 
bridge  limestones.  *  We  have  here  an  evidence  that  the  augmen- 
tation in  volume  observed  in  the  lower  members  of  the  Champlain 
division  in  the  Appalachian  region  extends  to  the  Trenton,  which 
to  the  west  of  Lake  Champlain  is  represented,  the  Chazy  included, 
by  not  more  than  500  feet  of  limestone.  The  Potsdam,  in  the  latter 
region,  consists  of  from  500  to  700  feet  of  sandstone  holding  Cono- 
cephalites  and  Lingulella,  and  overlaid  by  300  feet  of  magnesian 
limestone,  the  so-called  Calciferous  sandrock.  In  the  valley  of  the 
Mississippi  these  two  formations  in  Iowa,  Missouri,  and  Texas, 
are  represented  by  from  800  to  1300  feet  of  sandstones  and  mag- 
nesian limestones,  while  in  the  Black  Hills  of  Nebraska,  according 
to  Hayden,  the  only  representative  of  these  lower  formations  is 
about  one  hundred  feet  of  sandstone  holding  Potsdam  fossils.| 

In  striking  contrast  to  this  it  has  been  shown  that  along  the 
Appalachian  range  from  Newfoundland  to  Tennessee  these  lower 
formations  are  represented  by  from  8000  to  15000  feet  of  fossil- 
iferous  sediments.  It  has  been  suggested  by  Logan  that  these 
widely  differing  conditions  represent  deep-sea  accumulations  on 
the  one  hand,  and  the  deposits  from  a  shallow  sea  which  covered  a 
submerged  continental  plateau,  on  the  other  ;  the  sediments  in  the 
two  areas  being  characterized  by  a  similar  fauna,  though  differing 
greatty  in  lithological  characters  and  in  thickness.  To  this  we  may 
add  that  the  continental  area,  being  probabty  submerged  and  el- 
evated at  intervals,  became  overlaid  with  beds  which  represent 
only  in  a  partial  and  imperfect  manner  the  great  succession  of 
strata  which  were  being  accumulated  in  the  adjacent  ocean.  J 

In  a  paper  which  I  hope  to  present  to  the  geological  section 
during  the  present  meeting  of  the  Association  it  will  be  shown 
from  a  study  of  the  rocks  of  the  Ottawa  basin  that  the  typical 
Champlain  division  not  only  presents  important  paleontological 
breaks,  but  evidences  of  statigraphical  discordance  at  more  than 
one  horizon  over  the  continental  area,  which,  as  the  result  of 
widely  spread  movements,  might  be  supposed  to  be  represented  in 
the  Appalachian  region.  In  the  latter  Logan  has  already  observed 

*  Amer.  Jour.  Sci.,  227. 

f  Ibid.,  II,  xxv,  439,  xxxi,  234. 

I  Ibid.,  II,  xlvi,  225. 


24  ADDRESS    OF    T.    STERKY    HUNT. 

that  the  absence  of  all  but  the  highest  beds  of  the  Levis  along  the 
eastern  limit  of  the  Potsdam,  near  Swanton,  Vermont,  while  the 
whole  thickness  of  them  appears  a  little  farther  westward,  makes 
it  probable  that  there  is  a  want  of  conformity  between  the  two ; 
and  I  have  in  this  connection  insisted  upon  the  entire  absence  in 
this  locality  of  the  Calciferous,  which  is  met  with  a  little  farther 
south  in  the  section  just  mentioned,  as  another  evidence  of  the 
same  unconformity.*  There  are  also,  I  think,  reasons  for  sus- 
pecting another  stratigraphical  break  at  the  summit  of  the  Quebec 
group,  in  which  case  many  problems  in  the  geological  structure  of 
this  region  will  be  much  simplified. 

It  should  be  remembered  that  the  conditions  of  deposition  in 
some  areas  have  been  such  that  accumulations  of  strata,  corres- 
ponding to  long  geologic  periods,  and  elsewhere  marked  by  strati- 
graphical  breaks,  are  arranged  in  conformable  superposition  ;  and 
moreover  that  movements  of  elevation  and  depression  have  even 
caused  great  paleontological  breaks,  which  over  considerable  areas 
are  not  marked  by  any  apparent  discordance.  Thus  the  remarka- 
ble break  in  the  fauna  between  the  Calciferous  and  the  Chazy  is  not 
accompanied  by  any  noticeable  discordance  in  the  Ottawa  basin, 
and  in  Nebraska,  according  to  Hayden,  the  Potsdam,  Carbonifer- 
ous, Jurassic  and  Cretaceous  formations  are  all  represented  in 
about  1200  feet  of  conformable  strata. f  In  Sweden  the  whole 
series  from  the  base  of  the  Cambrian  to  the  summit  of  the  Upper 
Silurian  appears  as  a  conformable  sequence,  while  in  North  Wales, 
although  there  is  no  apparent  discordance  from  the  base  of  the 
Cambrian  to  the  summit  of  the  Lingula  flags,  stratigraphical 
breaks,  according  to  Ramsay,  probably  occur  both  at  the  base  and 
the  summit  of  the  Tremadoc  slates,  J  which  are  considered  equiva- 
lent to  the  Levis  formation. 

We  have  seen  that,  according  to  Logan,  a  dislocation  a  little  to 
the  north  of  Lake  Champlain  causes  the  Quebec  group  to  overlie 
the  higher  members  of  the  Champlain  division.  The  same  uplift, 
according  to  him,  brings  up,  farther  south,  the  Red  sandrock  of 
Vermont,  which  to  the  west  of  the  dislocation  rests  upon  the  up- 
turned and  inverted  strata  of  various  formations  from  the  Calcif- 
erous sandrock  to  the  Utica  and  Hudson  River  shales.  These 

*  Amer.  Jour.  Sci.,  II,  xlvi,  225. 

t  Ibid.,  II,  xxv,  440. 

J  Quar.  Geol.  Journal,  xix,  page  xxxvi. 


GEOGNOSY  OF  THE  APPALACHIANS.  25 

latter,  according  to  him,  are  seen  to  pass  for  considerable  distances 
beneath  nearly  horizontal  layers  of  the  Red  sandrock,  the  Utica 
slate,  in  one  case,  holding  its  characteristic  fossil,  Triartlirus  Beckii. 
This  relation,  which  is  well  shown  in  a  section  at  St.  Albans,  fig- 
ured by  Hitchcock,*  was  looked  upon  by  Emmons  and  by  Adams  as 
evidence  that  the  Red  sandrock  was  the  representative  of  the  Me- 
dina sandstone  of  the  New  York  system.  When,  however,  the 
former  had  recognized  the  Potsdam  age  of  the  sandrock,  with  its 
Olenellus,  which  he  supposed  to  be  Paradoxides,  this  condition  of 
things  was  conceived  to  be  an  evidence  of  the  existence  beneath 
the  Potsdam  of  an  older  and  unconformable  fossiliferous  series 
alread}'  mentioned. 

The  objections  made  by  Emmons  to  Rogers's  view  of  the  Cham- 
plain  age  of  the  Taconic  rocks  were  three-fold  :  first,  the  great  dif- 
ferences in  lithological  characters,  succession  and  thickness,  be- 
tween these  and  the  rocks  of  the  Champlain  division  as  previously 
known  in  New  York ;  second,  the  supposed  unconformable  infra- 
position  of  a  fossiliferous  series  to  the  Potsdam  ;  and  third,  the  dis- 
tinct fauna  which  the  Tacouic  rocks  were  supposed  to  contain.  The 
first  of  these  is  met  by  the  fact  now  established  that  in  the  Appa- 
lachian region,  the  Champlain  division  is  represented  by  rocks 
having,  with  the  same  organic  remains,  very  different  lithological 
characters,  and  a  thickness  ten-fold  greater  than  in  the  typical 
Champlain  region  of  northern  New  York.  The  second  objection 
has  already  been  answered  by  showing  that  the  rocks  which  pass 
beneath  the  Potsdam  are  realty  newer  strata  belonging  to  the  upper 
part  of  the  division,  and  contain  a  characteristic  fossil  of  the  Uti- 
ca slate.  As  to  the  third  point,  it  has  also  been  met,  so  far  as 
regards  the  Atops  and  Elliptocephalus,  by  showing  these  two 
genera  to  belong  to  the  Potsdam  formation.  If  we  inquire  farther 
into  the  Taconic  fauna  we  find  that  the  Stockbridge  limestone  (the 
Eolian  limestone  of  Hitchcock) ,  which  was  placed  by  Emmons  near 
the  base  of  the  Lower  Taconic,  (while  the  Olenellus  slates  are 
near  the  summit  of  the  Upper  Taconic),  is  also  fossiliferous,  and 
contains,  according  to  the  determinations  of  Professor  Hall,  species 
belonging  to  the  genera  Euomphalus,  Zaphrentis,  Stromatopora, 
Chaetetes  and  Stictopora.f  Such  a  fauna  would  lead  to  the  con- 


*  Geology  of  Vermont,  p.  374. 

t  Geology  of  Vermont,  419,  and  Amer.  Jour.  Sci.,  II,  xxxiii,  419. 


26  ADDRESS    OF    T.    STERRY    HUNT. 

elusion  that  these  limestones  instead  of  being  older,  were  really 
newer  than  the  Olenellus  beds,  and  that  the  apparent  order  of  suc- 
cession was,  contrary  to  the  supposition  of  Emmons,  the  true  one. 
This  conclusion  was  still  farther  confirmed  by  the  evidence  ob- 
tained in  1868  by  Mr.  Billings,  who  found  in  that  region  a  great 
number  of  characteristic  species  of  the  Levis  formation,  many  of 
,  them  in  beds  immediately  above  or  below  the  white  marbles,  * 
which  latter,  from  the  recent  observations  of  the  Rev.  Augustus 
Wing  in  the  vicinity  of  Rutland,  Vermont,  would  seem  to  be 
among  the  upper  beds  of  the  Potsdam  formation.  Thus  while 
some  of  the  Taconic  fossils  belong  to  the  Potsdam  and  Utica 
formations,  the  greater  number  of  them,  derived  from  beds  sup- 
posed to  be  low  down  in  the  system,  are  shown  to  be  of  the  age 
of  the  Levis  formation.  There  is,  therefore,  at  present,  no  evi- 
dence of  the  existence,  among  the  unaltered  sedimentary  rocks  of 
the  western  base  of  the  Appalachians  in  Canada  or  New  England, 
of  any  strata  more  ancient  than  those  of  the  Champlain  division, 
to  which,  from  their  organic  remains,  the  fossiliferous  Taconic 
rocks  are  shown  to  belong. 

Mr.  Billings  has,  it  is  true,  distinguished  provisionally  what  he 
has  designated  an  upper  and  a  lower  division  of  the  Potsdam,  and 
has  referred  to  the  latter  the  Red  sandrock  with  the  Olenellus 
slates  of  Vermont,  together  with  beds  holding  similar  fossils  at 
Troy,  New  York,  and  along  the  straits  of  Bellisle  in  Labrador  and 
Newfoundland ;  the  upper  division  of  the  Potsdam  being  repre- 
sented by  the  basal  sandstones  of  the  Ottawa  basin  and  of  the 
Mississippi  valley .f  In  the  present  state  of  our  knowledge  of 
the  local  variations  in  sediments  and  in  their  fauna  dependent  on 
depth,  temperature  and  ocean  currents,  Billings,  however,  con- 
ceives that  it  would  be  premature  to  assert  that  these  two  types  of 
the  Potsdam  do  not  represent  synchronous  deposits. 

The  base  of  the  Champlain  division,  as  known  in  the  Potsdam 
formation  of  New  York,  of  the  Mississippi  valley  and  the  Appa- 
lachian belt,  does  not,  however,  represent  the  base  of  the  paleozoic 
series  in  Europe.  The  Alum  slates  in  Sweden  are  divided  into 
two  parts,  an  upper  or  Olenus  zone,  and  a  lower  or  Conocoiyphe 
zone,  as  distinguished  by  Angelin.  The  latter  is  characterized  by 


*  Amer.  Jour.  Sci.,  II,  xlvi,  227. 

t  Report  Geol.  of  Canada,  1863-C6,  p.  236. 


GEOGNOSY  OF  THE  APPALACHIANS.  27 

the  genus  Paradoxides,  which  also  occupies  a  lower  division  in  the 
primordial  paleozoic  rocks  of  Bohemia  (Barrande's  stage  C), 
the  greater  part  of  which  are  regarded  as  the  equivalent  of  the 
Olenus  zone  of  Sweden  and  the  Potsdam  of  North  America.  The 
Lingula  flags  of  Wales  belong  to  the  same  horizon,  and  it  is  at 
their  base,  in  strata  once  referred  to  the  Lower  Lingula  flags,  that 
the  Paradoxides  is  met  with.  These  strata,  for  which  Hicks  and 
Salter,  in  1865,  proposed  the  name  of  the  Menevian  group,  are 
regarded  as  corresponding  to  the  lower  division  of  the  Alum  slates, 
and,  like  it,  contain  a  fauna  not  yet  recognized  in  the  basal  rocks 
of  the  Ne\v  York  s}Tstem.  We  here  approach  the  debatable  land 
between  the  Cambrian  and  the  Silurian  of  the  British  geologists. 
The  Cambrian,  as  originally  claimed  by  Sedgwick,  included  in  its 
upper  division  the  Middle  and  Upper  Lingula  flags,  with  the  over- 
lying Tremadoc  slates,  to  the  base  of  the  Llandeilo  rocks,  and  may 
be  regarded  as  equivalent  to  the  Potsdam,  Calciferous  and  Levis 
formations  ;  while  in  the  Lower  Cambrian  were  embraced  the  Lower 
Lingula  flags  and  the  Upper  and  Lower  Longmynd  rocks,  corres- 
ponding respectively  to  the  Harlech  grits  and  the  Llanberis  slates. 
A  portion  of  the  Cambrian  has,  however,  been  claimed  for  the 
Silurian  by  Murchison,  who  draws  the  dividing  line  at  the  top  of 
the  Longmynd  rocks,  leaving  the  three  divisions  of  the  Lingula 
flags  in  the  Silurian.  Lyell,  on  the  contrary,  remarks  that  {he 
Menevian  beds,  which  were,  on  lithological  grounds,  made  by 
Sedgwick  a  part  of  the  Lower  Lingula  flags,  have  been  shown 
by  Hicks  and  Salter  to  be  very  distinct  from  these  paleontologi- 
cally :  and,  while  he  includes  the  Menevian  in  the  Lower  Cam- 
brian, refers  the  whole  of  the  Lingula  flags  to  the  Upper  Cambrian. 
Lyell  therefore  admits  the  whole  of  the  Cambrian  system  as 
originally  defined  by  Sedgwick,  and  the  same  classification  is  now 
adopted  by  Linarsson,  in  Sweden,  where  in  Westrogothia,  the  Cam- 
brian rocks,  (resting  unconformabh-  on  the  c^stalline  schists  to  be 
noticed  farther  on),  are  overlaid  conformably  by  the  orthoceratite 
limestones,  which  are  by  him  regarded  as  forming  the  base  of  the 
Silurian,  and  as  the  equivalent  of  the  Llandeilo  rocks  of  Wales. 
The  total  thickness  of  these  lower  rocks  in  Sweden,  including  the 
representatives  of  the  Lingula  flags,  the  Menevian  beds  and  an 
underlying  fucoidal  (Eophyton)  sandstone,  is  only  three  hundred 
feet,  while  the  first  two  divisions  in  Wales  have  a  thickness  of 
five  to  six  thousand,  and  the  Harlech  grits  and  Llanberis  slates 


28  ADDRESS    OF   T.    STERRY   HUNT. 

(including  the  Welsh  roofing-slates  beneath)  amount  to  eight  thou- 
sand feet  additional.  Recent  researches  show  that  these  lower 
rocks  in  Wales  contain  an  abundant  fauna,  extending  downward 
some  2800  feet  from  the  Menevian  to  the  very  base  of  strata  re- 
garded as  the  representatives  of  the  Harlech  grits.  The  brachio- 
poda  of  the  Harlech  beds  appear  identical  with  those  of  the  Men- 
evian, but  new  species  of  Conocephalites,  Microdiscus  and  Para- 
doxides  are  met  with,  besides  a  new  genus,  Plutonia,  allied  to  the 
last  mentioned.  Mr.  Hicks,  to  whom  we  owe  these  discoveries,* 
remarks,  that  the  Menevian  gives  us,  for  the  present,  a  well 
marked  paleontological  horizon  for  the  summit  of  the  Cambrian, 
corresponding  with  the  Lower  Cambrian  as  defined  by  Sedgwick. 
The  Upper  Cambrian  in  North  America  would  thus  include  the 
lower  half  of  the  Champlain  division  from  the  base  of  the  Potsdam 
to  the  summit  of  the  Levis  (including  perhaps  the  Chazy),  while 
the  Lower  Cambrian,  (the  Cambrian  of  Murchison  and  Hicks)  is 
represented  by  the  strata  holding  Paradoxides  in  Newfoundland, 
New  Brunswick  and  eastern  Massachusetts.  Although  no  strata 
marked  by  these  fossils  have  yet  been  found  in  the  Appalachians, 
it  is  not  improbable  that  such  may  yet  be  met  with.  In  May, 
1861,  I  called  attention  to  the  fact  that  beds  of  quartzose  con- 
glomerate at  the  base  of  the  Potsdam  in  Hemmingford,  near  the 
outlet  of  Lake  Champlain  on  its  western  side,  contain  fragments 
of  green  and  black  slates,  "showing  the  existence  of  argillaceous 
slates  before  the  deposition  of  the  Potsdam  sandstone."  f  The 
more  ancient  strata,  which  furnished  these  slaty  fragments  to 
the  Potsdam  conglomerate,  have  perhaps  been  destroyed,  or  are 
concealed,  but  they  or  their  equivalents  may  yet  be  discovered 
in  some  part  of  the  great  Appalachian  region.  They  should 
not,  however,  be  called  Taconic,  but  receive  the  prior  designation 
of  Cambrian,  unless,  indeed,  it  shall  appear  that  the  source  of 
these  slate  fragments  was  the  more  argillaceous  beds  of  the  still 
older  Huronian  schists.  Emmons  regarded  his  Taconic  system 
as  the  equivalent  of  the  Lower  Cambrian  of  Sedgwick,  but  when 
in  1842,  Murchison  announced  that  the  name  of  Cambrian  had 
ceased  to  have  any  zoological  significance,  being  identical  with 
Lower  Silurian,!  Emmons,  conceiving,  as  he  tells  us,  that  all 

*Geol.  Mag.,  V,  306;  and  Rep.  Brit.  Assoc.,  3868,  p.  69;  also  Harkness  and  Hicks  in 
Nature,  Proc.  Geol.  Soc.,  May  10, 1871. 
t  Araer.  Jour.  Sci.,  II,  xxxi,  404. 
t  Proc.  Geol.  Soc.,  London,  III,  642. 


GEOGNOSY  OF  THE  APPALACHIANS.  29 

Cambrian  rocks  were  not  Silurian,  instead  of  maintaining  Sedg- 
wick's  name,  which  with  the  progress  of  paleontological  study  is 
assuming  a  great  zoological  importance,  devised  the  name  of 
Taconic,  as  s3Tnonymous.  with  Lower  Cambrian  ;  *  although,  as  we 
have  seen,  there  is  as  yet  no  paleontological  evidence  to  identify 
any  portion  of  the  Taconic  strata  with  the  well-defined  Lower 
Cambrian  rocks  of  our  eastern  shores. 

The  crystalline  infra- Silurian  strata,  to  which  the  name  of  the 
Huronian  series  has  been  given  by  the  Geological  Survey  of  Cana- 
da, have  sometimes  been  called  Cambrian  from  their  resemblance 
to  certain  rocks  in  Anglesea,  which  have  been  looked  upon  as  al- 
tered Cambrian.  The  typical  Cambrian  rocks  of  Wales,  down  to 
their  base,  are  however  uncrystalline  sediments,  and,  as  pointed  out 
b}T  Dr.  Bigsby  in  1863,  t  are  not  to  be  confounded  with  the  Huron- 
ian. which  he  regarded  as  equivalent  to  the  second  division  of  the 
so-called  azoic  rocks  of  Norway,  the  Urschiefer  or  primitive 
schists,  which  in  that  country  rest  unconformably  on  the  primitive 
gneiss  (Urgneiss),  and  are  in  their  turn  overlaid  unconformably  by 
the  fossiliferous  Cambrian  strata.  This  second  or  intermediate 
series  in  Norway  is  characterized  by  eurites,  micaceous,  chloritic 
and  hornblendic  schists,  with  diorites,  steatite  and  dark  colored 
serpentines,  generally  associated  with  chrome  ;  and  abounds  in  ores 
of  copper,  nickel  and  iron.  In  its  mineralogical  and  lithological 
characters,  the  Urschiefer  corresponds  with  what  we  have  desig- 
nated the  second  series  of  crystalline  schists.  It  is,  in  Norway, 
divided  into  a  lower  or  quartzose  division,  marked  by  a  predomi- 
nance of  quartzites,  conglomerates  and  more  massive  rocks,  and 
an  upper  and  more  schistose  division.  Macfarlane,  who  was  fami- 
liar with  the  rocks  of  Norway,  after  examining  both  the  Huronian 
of  Lake  Superior  and  the  crystalline  strata  of  the  Green  Moun- 
tains, had  already,  in  1862,  declared  his  opinion  that  both  of  these 
were  representatives  of  the  Norwegian  Urschiefer,  J  thus  anticipa- 
ting, from  his  comparative  studies,  the  conclusions  of  Bigsby. 

The  crystalline  rocks  of  Anglesea  and  the  adjacent  part  of 
Caernarvon,  which  have  been  described  and  mapped  b}'  the  British 
Geological  Survey  as  altered  lowest  Cambrian,  are  directly  over- 
laid by  strata  of  the  Llandeilo  and  Bala  divisions,  corresponding 

*  Emmons,  Geol.  N.  District  of  New  York,  162 ;  and  Agric.  of  New  York,  I,  49. 
t  Quar.  Jour.  Geol.  Soc.,  XIX,  36. 
J  Canadian  Naturalist,  VII,  125. 


30  ADDRESS    OF   T.    STERRY   HUNT. 

to  the  Trenton  and  Hudson  River  formations.  If  we  consult 
Ramsay's  report  on  the  region,  it  will  be  found  that  he  speaks  of 
them  as  "probably  Cambrian,"  and  states  as  a  reason  for  that 
opinion,  that  they  are  connected  by  certain  beds  of  intermediate 
lithological  characters  with  strata  of  undoubted  Cambrian  age.* 
These,  however,  as  he  admits,  present  great  local  variations,  and, 
after  carefully  scanning  the  whole  of  the  evidence  adduced,  I  am 
inclined  to  see  in  it  nothing  more  than  the  existence,  in  this 
region,  of  Cambrian  strata  made  up  from  the  ruins  from  the  great 
mass  of  pre-Cambrian  schists,  which  are  the  crystalline  rocks  of 
Anglesea.  Such  a  phenomenon  is  repeated  in  numerous  instances 
in  our  North  American  rocks,  and  is  the  true  explanation  of  many 
supposed  examples  of  passage  from  crystalline  schists  to  imcrys- 
talline  sediments.  The  Anglesea  rocks  are  a  highly  inclined  and 
much  contorted  series  of  quartzose,  micaceous,  chloritic  and  epi- 
dotic  schists,  with  diorites  and  dark  colored  chromiferous  serpen- 
tines, all  of  which,  after  a  careful  examination  of  them  in  the 
collections  of  the  Geological  Survey  of  Great  Britain,  appear  to 
me  identical  with  the  rocks  of  the  Green  Mountain  or  Huronian 
series.  A  similar  view  of  their  age  is  shared  by  Phillips  and  by 
Sedgwick,  in  opposition  to  the  opinion  of  the  British  survey.  The 
former  asserts  that  the  crystalline  schists  of  Anglesea  are  "  below 
all  the  Cambrian  rocks  ;"f  while  Sedgwick  expresses  the  opinion 
that  they  are  of  "  a  distinct  epoch  from  the  other  rocks  of  the  dis- 
trict, and  evidently  older.";}; 

Associated  with  the  fossiliferous  Devonian  rocks  of  the  Rhine, 
is  a  series  of  crystalline  schists,  similar  to  those  just  noticed,  seen 
in  the  Taunus,  the  Hundsriick  and  the  Ardennes.  These,  in  oppo- 
sition to  Dumont,  who  regarded  them  as  belonging  to  an  older 
system,  are  declared  by  Romer  to  have  resulted  from  a  subsequent 
alteration  of  a  portion  of  the  Devonian  sediments.  § 

Turning  now  to  the  Highlands  of  Scotland,  we  have  a  similar 
series  of  crystalline  schists,  presenting  all  the  mineralogical  char- 
acters of  those  of  Norway  and  of  Anglesea,  which,  according  to 
Murchison  and  Giekie,  are  neither  of  Cambrian  nor  pre-Cambrian 
age,  but  are  younger  than  the  fossiliferous  limestones  of  the  west- 

*Geol.  of  North  Wales,  pp.  145, 175. 

t  Manual  of  Geology  (1855)  89. 

t  Geol.  Journal  for  1845,  449. 

§  Naumann,  Geognosie,  2d  edition,  II,  383. 


GEOGNOSY  OF  THE  APPALACHIANS.  31 

ern  coast  (about  the  horizon  of  the  Levis  formation)  which  seem 
to  pass  beneath  them.  Professor  Nicol,  on  the  contrary,  maintains 
that  this  apparent  super-position  is  due  to  uplifts,  and  that  these 
crystalline  schists  are  really  older  than  either  Cambrian  or  Silurian, 
both  of  which  appear  to  the  west  of  them  as  uncrystalline  sedi- 
ments, resting  on  the  Laurentian.  He  does  not,  however,  con- 
found these  crystalline  schists  of  the  Scottish  Highlands  with  the 
Laurentian,  from  which  they  differ  mineralogically,  but  regards 
them  as  a  distinct  series.*  In  the  presence  of  the  differences  of 
opinion  which  have  been  shown  in  this  controversy,  we  may  be 
permitted  to  ask  whether,  in  such  a  case,  stratigraphical  evidence 
alone  is  to  be  relied  upon.  Repeated  examples  have  shown  that 
the  most  skilful  stratigraphists  may  be  misled  in  studying  the 
structure  of  a  disturbed  region  where  there  are  no  organic  remains 
to  guide  them,  or  where  unexpected  faults  and  overslides  may 
deceive  even  the  most  sagacious.  I  am  convinced  that  in  the 
study  of  the  crystalline  schists,  the  persistence  of  certain  mineral 
characters  must  be  relied  upon  as  a  guide,  and  that  the  language 
used  by  Delesse,  in  1847,  will  be  found  susceptible  of  a  wide  ap- 
plication to  crystalline  strata.  "Rocks  of  the  same  age  have 
most  generally  the  same  chemical  and  mineralogical  composition, 
and  reciprocally,  rocks  having  the  same  chemical  composition  and 
the  same  minerals,  associated  in  the  same  manner,  are  of  the  same 
age."t 

In  this  connection  the  testimony  of  Professor  James  Hall  is  to 
the  point.  Speaking  of  the  crystalline  schists  of  the  White  Moun- 
tain series,  he  says  :  — 

"  Every  observing  student  of  one  or  two  years  experience  in  the 
collection  of  minerals  in  the  New  England  States,  knows  well  that 
he  may  trace  a  mica-schist  of  peculiar  but  varying  character  from 
Connecticut,  through  central  Massachusetts,  and  thence  into  Ver- 
mont and  New  Hampshire,  by  the  presence  of  staurolite  and  some 
other  associated  minerals,  which  mark  with  the  same  unerring  cer- 
tainty the  geological  relations  of  the  rock  as  the  presence  of  Pen- 
tamerus  oblongus,  P.  galeatus,  Spirifer  Xiagarensis.  or  #.  macro- 
pleura,  and  their  respectively  associated  fossils  do  the  relations  of 
the  several  rocks  in  which  these  occur."  J 

*Quar.  Jour.  Geol.  Soc.;  Murchison,  XV,  353;  Giekie,  XVII,  171;  Nicol,  XVII,  58, 
XVIII,  443. 

t  Bull.  Soc.  Geol.  de  Fr.  (2),  IV,  786. 

t  Paleontology  of  New  York,  Vol.  Ill,  Introduction,  page  93. 


32  ADDRESS    OF    T.    STERRY    HUNT. 

I  am  convinced  that  these  crystalline  schists  of  Germany,  Angle- 
sea,  and  the  Scotch  Highlands,  will  be  found,  like  those  of  Nor- 
wajr,  to  belong  to  a  period  anterior  to  the  deposition  of  the 
Cambrian  sediments,  and  will  correspond  with  the  newer  gneissic 
jseries  of  our  Appalachian  region.  There  exists,  in  the  Highlands 
of  Scotland,  a  great  volume  of  fine-grained,  thin-bedded  mica- 
schists  with  andalusite,  staurolite  and  cyanite,  which  are  met  with 
in  Argyleshire,  Aberdeenshire,  Banffshire  and  the  Shetland  Isles. 
Rocks  regarded  by  Harkness  as  identical  with  these  of  the  Scottish 
Highlands  also  occur  in  Donegal  and  Mayo  in  Ireland.  Through 
the  kindness  of  the  Rev.  Prof.  Haughton  of  Trinity  College,  and 
Mr.  Robert  H.  Scott,  then  of  Dublin,  I  received  some  years  since, 
a  large  collection  of  the  crystalline  rocks  of  Donegal,  which 
I  am  thus  enabled  to  compare  with  those  of  North  America,  and 
to  assert  the  existence  in  the  northwest  of  Ireland,  of  our  second 
and  third  series  of  crystalline  schists.  The  Green  Mountain  rocks 
are  there  exactly  represented  by  the  dark  colored  chromiferous 
serpentines  of  Aghadoey,  and  the  steatite,  crystalline  talc  and 
actinolite  of  Crohy  Head;  while  the  mica-schist  of  Loch  Derg, 
with  white  quartz,  blue  cyanite,  staurolite  and  garnet,  all  united 
in  the  same  fragment,  cannot  be  distinguished  from  specimens 
found  at  Cavendish,  Vermont,  and  Windham,  Maine.  The  fine- 
grained andalusite-schists  of  Clooney  Lough  are  exactly  like 
those  from  Mount  Washington ;  while  the  granitoid  mica-slates 
from  several  other  localities  in  Donegal  are  not  less  clearly  of  the 
type  of  the  White  Mountain  series.  Similar  micaceous  schists, 
with  andalusite  (chiastolite) ,  occur  on  Skiddaw,  in  Cumberland, 
England,  the  relations  of  which  have  been  clearly  defined  by  Sedg- 
wick,  who  groups  the  rocks  of  Skiddaw  into  four  divisions.  The 
lowest  of  these,  succeeding  the  granite,  is  a  series  of  crystalline 
rocks,  not  described  lithologically,  with  mineral  veins,  "  having 
some  resemblance  to  the  rocks  of  Cornwall,"  and  including 
towards  the  summit,  "  chiastolite  schists  and  chiastolite  rocks." 
These  are  followed  in  ascending  order  by  two  great  series  of  slates 
and  grits,  succeeded  by  a  fourth  division  of  schists,  sometimes 
carbonaceous,  holding  in  parts  fucoids  and  graptolites,  which  are 
apparently  overlaid  discordantly  by  sundry  trappean  conglomer- 
ates and  chloritic  slates.*  The  graptolites  of  the  Skiddaw  slates 

*  Synopsis  of  British  Paleozoic  Rocks,  p.  Ixxxiv,  being  an  introduction  to  McCoy's 
Brit.  Pal.  Fossils  (1855). 


GEOGNOSY  OF  THE  APPALACHIANS.  33 

are  found  to  be  identical  with  those  of  the  Levis  formation,*  and 
it  is  worthy  of  notice  that  although  Sedgwick  places  the  mica- 
schists  with  andalusite  (chiastolite)  so  far  below  the  graptolitic 
beds,  he  elsewhere,  in  comparing  the  rocks  of  North  Wales  and 
Cumberland,  states  that  the  chloritic  and  micaceous  rocks  of 
Anglesea  and  Caernarvon  are  not  represented  in  Cumberland, 
being  distinct  from  the  other  rocks  of  North  Wales,  and  much 
older.f 

In  Victoria,  Australia,  the  position  of  the  chiastolite  schists,  ac- 
cording to  Selwyn,  is  beneath  the  graptolitic  slates.  Boblaye,  it 
is  true,  asserted  in  1838  that  the  chiastolite  schists  of  Les  Salles. 
near  Pontivy  in  Brittany,  include  Orthis  and  Calymene,  J  but  when 
we  remember  that  even  experienced  observers  in  the  White  Moun- 
tains for  a  time  mistook  for  remains  of  Crustacea  and  brachiopods. 
certain  obscure  forms,  which  they  afterwards  found  not  to  be 
organic,  and  that  Dana,  in  this  connection,  has  called  attention  to 
the  deceptive  resemblance  to  fossils  presented  by  some  imperfectly 
developed  chiastolite  crystals  in  the  same  region,  §  we  may  well 
require  a  verification  of  Boblaye's  observation,  especially  since  we 
find  that  more  recently  D'Archiac  and  Dalimier  agree  with  De 
Beaumont  and  Dufrenoy  in  placing  the  chiastolite  schists  of 
Brittany  at  the  very  base  of  the  transition  sediments,  marking  the 
summit  of  the  crystalline  schists.  || 

With  regard  to  the  crystalline  schists  of  Lakes  Huron  and  Su- 
perior, to  which  the  name  of  the  Huronian  system  has  been  given, 
the  observations  of  all  who  have  studied  the  region  concur  in  plac- 
ing them  unconformably  beneath  the  sediments  which  are  supposed 
to  represent  the  base  of  the  New  York  system,  while,  on  the  other 
hand,  they  rest  unconformably  on  the  Laurentian  gneiss,  fragments 
of  which  are  included  in  the  Huronian  conglomerates.  The  gneissic 
series  of  the  Green  Mountains  had,  however,  as  we  have  seen,  been, 
since  1841,  regarded  by  the  brothers  Rogers,  Mather,  Hall,  Hitch- 
cock, Adams,  Logan,  myself  and  others,  as  of  Silurian  age.  Eaton 
and  Emmons  had  alone  claimed  for  it  a  pre-Cambrian  age  until,  in 
1862,  Macfaiiane  ventured  to  unite  it  with  the  Huronian  system. 


*Harkness  and  Salter,  Quar.  Jour.  Geol.  Soc.,  xix,  135. 
t  Geol.  Journal  (1845),  IV,  583. 
J  Bull.  Soc.  Geol.  de  FT.,  X,  227. 
§  Amer.  Jour.  Sci.,  II,  i,  415,  v,  116. 
||  Bull.  Soc.  Geol.  de  Fr.,  H,  xviii,  664. 

AMER  NAT.,   ASSOC.    NUMBER.  3 


34  ADDRESS    OF    T.    STERRY   HUNT. 

• 

and  to  identify  both  with  the  crystalline  schists  of  a  similar  age  in 
Norway.  Later  observations  in  Michigan  justify  still  farther  this 
comparison,  for  not  only  the  more  schistose  beds  of  the  Green  Moun- 
tain series,  but  even  the  mica-schists  of  the  third  or  White  Mountain 
series,  with  staurolite  and  garnet,  are  represented  in  Michigan,  as 
appears  by  the  recent  collections  of  Major  Brooks,  of  the  Geolog- 
ical Survey  of  Michigan,  kindly  placed  in  my  hands  for  examina- 
tion. He  informs  me  that  these  latter  schists  are  the  highest  of 
the  crystalline  strata  in  the  northern  peninsula. 

To  the  north  of  Lake  Superior,  as  I  have  already  shown  else- 
where, the  schists  of  this  third  series,  which,  as  early  as  1861,  I 
compared  to  those  of  the  Appalachians,  are  widely  spread ;  while 
in  Hastings  County,  forty  miles  north  of  Lake  Ontario,  rocks  hav- 
ing the  mineralogical  and  lithological  characters  both  of  the 
second  and  third  series  are  found  resting  on  the  first  or  Lauren- 
tian,  the  three  apparently  unconformable,  and  all  in  turn  overlaid 
by  horizontal  Trenton  limestone.* 

We  have  shown,  that  in  Pennsylvania,  while  some  of  these  schists 
of  the  second  and  third  series  were  regarded  as  altered  primal 
rocks  by  H.  D.  Rogers,  others,  lithologicalty  similar,  were  referred 
by  him  to  the  older  so-called  azoic  series,  which  we  believe  to  be 
their  true  position.  Professor  W.  B.  Rogers  has  lately  informed 
me  that  in  Virginia  the  gneissic  series  having  the  characters  of 
the  Green  Mountain  rocks,  is  clearly  overlaid  unconformably  by  the 
lowest  primal  paleozoic  strata  of  the  region.  Coming  northward, 
the  uncrystalline  argillites  and  sandstones  holding  Paradoxides  at 
Braintree,  Massachusetts,  f  and  St.  John,  New  Brunswick,  overlie 
unconformably  crystalline  schists  of  the  second  series,  and  in  the 
latter  region,  in  one  locality,  rocks  which  are  by  Bailey  and  Mat- 
thew regarded  of  Laurentian  age.  In  Newfoundland,  in  like 
manner,  a  great  series  of  crystalline  schists,  in  which  Mr.  Murray 
recognizes  the  Huronian  system  as  first  studied  and  described  by 
him  in  the  west,  is  unconformably  overlaid  by  a  group  of  sand- 
stones, limestones,  and  slates  holding  Paradoxides.  The  peculiar 
gneisses  and  mica-schists  of  the  White  Mountain  series  appear  to 
be  developed  to  a  great  extent  in  Newfoundland,  which  has  led 
me  to  propose  for  them  the  name  of  the  Terranovan  system,  j 

*  Amer.  Jour.  Sci.,  TI,  xxxi,  395,  and  1,  85. 
fHunt,  Proc.  Bost.  Nat.  Hist.  Soc.,  Oct.,  19, 1870. 
t  Amer.  Jour.  Sci.,  II,  1,  87. 


GEOGNOSY  OF  THE  APPALACHIANS.  35 

* 

From  the  part  which  the  ruins  of  these  rocks  play  in  the  produc- 
tion of  succeeding  sediments  it  is  not  always  easy  to  define  the  limits 
between  the  ancient  mica-schists  and  the  Cambrian  strata  in  these 
northeastern  regions.  It  is  not  impossible  that  the  two  may  grad- 
uate into  each  other,  as  some  have  supposed,  in  Newfoundland  and 
Nova  Scotia,  but  until  farther  light  is  thrown  upon  the  subject  I 
am  disposed  to  regard  the  relation  between  the  two  as  one  of  der- 
ivation rather  than  of  passage. 

We  have  already  alluded  to  the  history  of  the  rocks  of  the 
White  Mountains,  formerly  looked  upon  as  primary,  and  by  Jack- 
son described  as  an  old  granitic  and  gneissic  axis  uplifting  the  more 
recent  Green  Mountain  rocks.  Their  manifest  differences  from  the 
more  ancient  gneiss  of  the  Adirondacks,  and  their  apparent  super- 
position to  the  Green  Mountain  series,  then  regarded  by  the 
Messrs.  Rogers  as  belonging  to  the  Champlain  division,  led  them 
in  1846  to  look  upon  the  White  Mountains  as  altered  strata  be- 
longing to  the  Levant  division  of  their  classification,  correspond- 
ing to  the  Oneida,  Medina  and  Clinton  of  the  New  York  system. 
In  1848  Sir  William  Logan  came  to  a  somewhat  similar  conclusion. 
Accepting,  as  we  have  seen,  the  view  of  Emmons  that  the  strata 
about  Quebec  included  a  portion  of  the  Levant  division,  and  re- 
garding the  Green  Mountain  gneisses  as  the  equivalents  of  these, 
he  was  induced  to  place  the  White  Mountain  rocks  still  higher  in 
the  geological  series  than  the  Messrs.  Rogers  had  done,  and  ex- 
pressed his  belief  that  they  might  be  the  altered  representatives 
of  the  New  York  system  from  the  base  of  the  Lower  Helderberg 
to  the  top  of  the  Chemung ;  in  other  words,  that  they  were  not 
Middle  Silurian,  but  Upper  Silurian  and  Devonian.  This  view, 
adopted  and  enforced  by  me,*  was  farther  supported  by  Lesley  in 
1860,  and  has  been  generally  accepted  up  to  this  time.  In  1870, 
however,  I  ventured  to  question  it,  and  in  a  published  letter  ad- 
dressed to  Professor  Dana,  concluded  from  a  great  number  of 
facts  that  there  exists  a  system  of  crystalline  schists  distinct  from, 
and  newer  than,  the  Laurentian  and  Huronian,  to  which  I  gave  the 
provisional  name  of  Terranovan,  constituting  the  third  or  White 
Mountain  series,  which  appears  not  only  throughout  the  Appalach- 
ians, but  westward  to  the  north  of  Lake  Ontario,  and  around  and 
beyond  Lake  Superior,  f  Although  I  have  in  common  with  most 

*  Geol.  Survey  of  Canada,  Report  1847-48,  p.  58;  also  Amer.  Jour.  Sci.,  II,  ix,  19. 
t  Amer.  Jour.  Sci.,  II,  1,  83. 


36  ADDRESS    OF   T.    STERRY   HUNT. 

other  American  geologists,  maintained  that  the  crystalline  rocks 
of  the  Green  Mountain  and  White  Mountain  series  are  altered 
paleozoic  sediments,  I  find,  on  a  careful  examination  of  the  evi- 
dence, no  satisfactory  proof  of  such  an  age  and  origin,  but  an 
array  of  facts  which  appear  to  me  incompatible  with  the  hitherto 
received  view,  and  lead  me  to  conclude  that  the  whole  of  our  crys- 
talline schists  of  eastern  North  America  are  not  only  pre-Silurian 
but  pre-Cambrian  in  age. 

In  what  precedes,  I  have  endeavored  to  discuss  briefly  and 
impartially  some  of  the  points  in  the  history  of  the  older  rocks, 
and  of  the  views  which  during  the  past  thirty  years  have  been 
entertained  as  to  their  age  and  geological  relations,  both  in  Amer- 
ica and  in  Europe.  I  have  said  some  things  which  will  provoke 
criticism,  and  at  the  same  time,  I  trust,  lead  to  farther  study  of 
these  rocks,  a  correct  knowledge  of  which  lies  at  the  basis  of 
geological  science. 

I  cannot,  however,  conclude  this  part  of  my  subject  without 
referring  to  the  views  put  forth  in  1869  by  Professor  Hermann 
Credner  of  Leipzig,  in  an  essay  on  the  Eozoic  or  pre-Silurian  for- 
mations of  North  America.*  With  Macfarlane,  he  refers  to  the 
Huronian  the  gneissic  series  of  the  Green  Mountains,  but  includes 
with  it,  as  part  of  the  Huronian  system,  the  so-called  Lower  Ta- 
conic  rocks  of  Vermont,  "with  remains  of  annelids  and  crinoids." 
Credner  thus  falls  into  the  very  error  against  which  Emmons 
warned  American  geologists,  namely,  the  confounding  in  one  sys- 
tem the  ancient  crystalline  schists  with  the  newer  fossiliferous 
sediments.  Resting  unconformably  on  these,  he  places,  first,  the 
Upper  Taconic,  corresponding,  according  to  him,  to  a  part  of  the 
Quebec  group,  and  second,  the  Potsdam  sandstone.  In  this  he 
has  copied,  for  the  most  part,  Marcou,  who,  however,  groups  the 
whole  of  these  various  divisions  in  the  Taconic  system,  while 
Credner,  rejecting  the  name,  unites  a  portion  of  the  Taconic  of 
Emmons  with  the  Huronian  system,  and  refers  the  other  portion, 
together  with  the  Potsdam,  to  the  Silurian.  These  same  views  are 
set  forth  in  a  more  recent  paper,  by  the  same  author,  on  the  Alle- 
ghany  system,  which  is  accompanied  with  sections  and  a  geologi- 
cally colored  map.|  In  this,  not  content  with  including  in  the 
Huronian  both  the  fossiliferous  strata  of  the  Levis  formation  and 

*Die  Gliederung  der  Eozoischen  Fonnationsgruppe,  u.  s.  w.,  pp.  53.    Halle,  1869. 
fPetermann's  Geographische  Mittheilungen.    2  Heft,  1871 . 


GEOGNOSY  OF  THE  APPALACHIANS.  37 

the  crystalline  schists  of  the  Green  Mountains,  he  refers  the 
gneisses  and  mica-schists  of  the  White  Mountains  to  the  same 
system ;  while  the  broad  area  of  similar  rocks  from  their  base  to 
the  sea  at  Portland,  is  regarded  as  Laurentian.  This,  on  Credner's 
map,  is  also  made  to  include,  with  the  exception  of  the  White 
Mountains  themselves,  all  the  rocks  of  the  third  or  White  Moun- 
tain series  which  cover  so  large  a  part  of  New  England.  Those 
who  have  followed  the  historical  sketch  already  given,  can  see  how 
widely  these  notions  of  Credner  differ  from  those  of  Emmons,  and 
from  all  other  American  geologists,  and  how  much  they  are  at 
variance  with  the  present  state  of  our  knowledge.  It  is  much  to 
be  regretted  that  so  good  a  geologist  and  lithologist  should,  from 
a  too  superficial  study,  Jiave  fallen  into  these  errors,  which  can 
only  retard  the  progress  of  comparative  geognosy,  for  which  he 
has  done  so  much.  In  England,  again,  Credner  confounds  the 
Cambrian  and  Huronian.  referring  to  the  latter  system  the  whole 
of  the  Longmynd  rocks  with  their  characteristic  Cambrian  fauna, 
a  view  which  is  supported  only  by  the  conjectured  Cambrian  age 
of  the  crystalline  schists  of  Anglesea,  which  are  probably  pre- 
Cambrian  and  veritably  Huronian,  like  the  Urschiefer  of  Scan- 
dinavia ;  which  Credner  correctly  refers  to  the  latter  system,  as 
Macfarlane  and  Bigsby  had  done  before  him.  He,  moreover,  rec- 
ognizes in  the  similar  crystalline  schists  of  Scotland,  the  Urals, 
and  various  parts  of  Germany,  including  those  of  Bavaria  and 
Bohemia,  a  newer  system,  overlying  the  primary  or  Laurentian 
gneiss,  and  corresponding  to  the  Huronian  or  Green  Mountain 
series  of  North  America,  while  he  suggests  a  correspondence  with 
similar  rocks  in  Japan,  Bengal,  and  Brazil.  In  a  collection  of 
rocks  brought  from  the  latter  country  by  Professor  C.  F.  Hartt,  I 
have  found,  as  elsewhere  stated,*  what  appear  to  be  representa- 
tives of  the  three  types  of  crystalline  schists  which  have  been 
distinguished  in  eastern  North  America. 

It  will  be  noticed  that  I  have  not,  in  the  preceding  pages, 
referred  to  the  Labradorian  (Upper  Laurentian)  system,  which  is 
characterized  by  a  great  predominance  of  norites  and  hyperites. 
Although  occupying  a  considerable  area  in  the  Adirondack  region, 
it  is  not  certainly  known  in  the  Appalachian  range,  and  was, 
therefore,  omitted  in  the  discussion.  In  addition  to  the  facts 

*The  Nation,  Dec.  1, 1870,  and  Hartt's  Geology  of  Brazil,  p.  550. 


38  ADDRESS    OF   T.    STERRY   HUNT. 

given  by  me  in  1869,*  it  may  be  added  that  the  observations  of 
Mr.  Richardson,  during  that  season,  on  the  north  side  of  the  Gulf 
of  St.  Lawrence,  confirm  the  previous  conclusions,  and  show  that 
the  rocks  of  the  Labradorian  (or  rather  Norian)  system  there  re- 
pose transgressively,  and  often  at  comparatively  moderate  angles, 
on  the  nearly  vertical  Laurentian  gneisses. |  We  may,  I  think,  in 
the  present  state  of  our  knowledge,  regard  these  norites  or  .Norian 
rocks  as  portions  of  a  pre-Huronian  system. 

II.     The  Origin  of  Crystalline  Rocks. 

We  now  approach  the  second  part  of  our  subject,  namely,  the 
genesis  of  the  crystalline  schists  whose  history  we  have  just  dis- 
cussed. The  origin  of  the  mineral  silicates  which  make  up  a  great 
portion  of  the  crystalline  rocks  of  the  earth's  surface  is  a  ques- 
tion of  much  geological  interest,  which  has  been  to  a  great  degree 
overlooked.  The  gneisses,  mica-schists  and  argillites  of  various 
geological  periods  do  not  differ  very  greatly  in  chemical  constitu- 
tion from  modern  mechanical  sediments,  and  are  now  very  gene- 
rally regarded  as  resulting  from  a  molecular  re-arrangement  of 
similar  sediments  formed  in  earlier  times  by  the  disintegration 
of  previously  existing  rocks  not  very  unlike  them  in  composition  ; 
the  oldest  known  formations  being  still  composed  of  crystalline 
stratified  deposits  presumed  to  be  of  sedimentary  origin.  Before' 
these  the  imagination  conceives  yet  earlier  rocks,  until  we  reach 
the  surface  of  unstratified  material  which  the  globe  may  be  sup- 
posed to  have  presented  before  water  had  begun  its  work.  It  is 
not,  however,  my  present  plan  to  consider  this  far-off  beginning  of 
sedimentary  rocks,  which  I  have  elsewhere  discussed.  \ 

Apart  from  the  clay  and  sand-rocks  just  referred  to,  whose  com- 
position maybe  said  to  be  essentially  quartz  and  aluminous  silicates, 
chiefly  in  the  forms  of  feldspars  and  micas,  or  the  results  of  their 
partial  decomposition  and  disintegration,  there  is  another  class 
of  crystalline  silicated  rocks  which,  though  far  less  important  in 
bulk  than  the  last,  is  of  great  and  varied  interest  to  the  litholo- 
gist,  the  mineralogist,  the  geologist  and  chemist.  The  rocks  of 
this  second  class  may  be  defined  as  consisting  in  great  part  of  the 
silicates  of  the  protoxyd  bases,  lime,  magnesia  and  ferrous  oxyd, 

*On  Norites,  etc.,  Amer.  Jour.  Sci.,  II,  xlviii,  180. 
t  Geol.  Survey  of  Canada,  Report  1866-69,  p.  306. 
$  Amer.  Jour.  Science,  II,  1,  25. 


ORIGIN    OF   CRYSTALLINE    ROCKS.  39 

either  alone,  or  in  combination  with  silicates  of  alumina  and  alka- 
lies. They  include  the  following  as  their  chief  constituent  mineral 
species: — pyroxene,  hornblende,  olivine,  serpentine, talc,  chlorite, 
epidote,  garnet  and  triclinic  feldspars  such  as  labradorite.  The 
great  types  of  this  second  class  are  not  less  well  defined  than 
the  first,  and  consist  of  pyroxenic  and  hornblendic  rocks,  passing 
into  diorites,  diabases,  ophiolites  and  talcose,  chloritic  and  epi- 
dotic  rocks.  Intermediate  varieties  resulting  from  the  associa- 
tion of  the  minerals  of  this  class  with  those  of  the  first,  and  also 
with  the  materials  of  non-silicated  rocks,  such  as  limestones  and 
dolomites,  show  an  occasional  blending  of  the  conditions  under 
which  these  various  types  of  rocks  were  formed. 

The  distinctions  just  drawn  between  the  two  great  divisions  of  sil- 
icated  rocks,  are  not  confined  to  stratified  deposits,  but  are  equally 
well  marked  in  eruptive  and  unstratified  masses,  among  which  the 
first  type  is  represented  by  trachytes  and  granites,  and  the  second, 
by  dolerites  and  diorites.  This  fundamental  difference  between 
acid  and  basic  rocks,  as  the  two  classes  are  called,  finds  its  ex- 
pression in  the  theories  of  Phillips,  Durocher  and  Bunsen,  who 
have  deduced  all  silicated  rocks  from  two  supposed  layers  of  molt- 
en matter  within  the  earth's  crust,  consisting  respectively  of  acid 
and  basic  mixtures  ;  the  trachytic  and  pyroxenic  magmas  of  Bunsen. 
From  these,  by  a  process  of  partial  crystallization  and  eliquation, 
or  by  commingling  in  various  proportions,  those  eruptive  rocks 
which  depart  more  or  less  from  the  normal  types,  are  supposed  by 
the  theorists  of  this  school  to  be  generated.*  The  doctrine  that 
these  eruptive  rocks  are  not  derived  direct^  from  a  hitherto  uncon- 
gealed  nucleus,  but  are  softened  and  crystallized  sediments,  in  fact 
that  the  whole  of  the  rocks  at  present  known  to  us  have  at  one 
time  been  aqueous  deposits,  has,  however,  found  its  advocates.  In 
support  of  this  view,  I  have  endeavored  to  show  that  the  natural 
result  of  forces  constantly  in  operation,  tends  to  resolve  the  various 
igneous  rocks  into  two  classes  of  sediments,  in  which  the  two  types 
are,  to  a  great  extent,  preserved.  The  mechanical  and  chemical 
agencies  which  transform  the  crystalline  rocks  into  sediments,  sepa- 
rate these  more  or  less  completely  into  coarse,  sandy,  permeable 
beds  on  the  one  hand,  and  fine  clayey  impervious  muds  on  the  other. 
The  action  of  infiltrating  atmospheric  waters  on  the  first  and  more 
silicious  strata,  removes  from  them  lime,  magnesia,  iron-oxj'd  and 
*Uunt  on  Some  Points  of  Chemical  Geology,  Quar.  Jour.  Geol.  Soc.,  XV,  489. 


40  ADDRESS    OF   T.    STERRY   HUNT. 

soda,  leaving  behind  silica,  alumina  and  potash  —  the  elements  of 
granitic,  gneissic  and  trachytic  rocks.  The  finer  and  more  alumi- 
nous sediments,  including  the  ruins  of  the  soft  and  easily  abraded 
silicates  of  the  pyroxene  group,  resisting  the  penetration  of  the 
water,  will,  on  the  contrary,  retain  their  alkalies,  lime,  magnesia 
and  iron,  and  thus  will  have  the  composition  of  the  more  basic 
rocks.  * 

A  little  consideration  will,  however,  show  that  this  process,  al- 
though doubtless  a  true  cause  of  differences  in  the  composition  of 
sedimentary  rocks,  is  not  the  only  one,  and  is  inadequate  to  ex- 
plain the  production  of  many  of  the  varieties  of  stratified  silicated 
rocks.  Such  are  serpentine,  steatite,  hornblende,  diallage,  chlorite, 
pinite  and  labradorite,  all  of  which  mineral  species  form  rock-masses 
by  themselves,  frequently  almost  without  admixture.  No  geologi- 
cal student  will  now  question  that  all  of  these  rocks  occur  as 
members  of  stratified  formations.  Moreover,  the  manner  in  which 
serpentines  are  found  interstratified  with  steatite,  chlorite,  argillite, 
diorite,  hornblende  and  feldspar  rocks,  and  these,  in  their  turn, 
with  quartzites  and  orthoclase  rocks,  is  such  as  to  forbid  the  notion 
that  these  various  materials  have  been  deposited,  with  their  present 
composition,  as  mechanical  sediments  from  the  ruins  of  preexist- 
ing rocks ;  a  hypothesis  as  untenable  as  that  ancient  one  which 
supposed  them  to  be  the  direct  results  of  plutonic  action. 

There  are,  however,  two  other  hypotheses  which  have  been  pro- 
posed to  explain  the  origin  of  these  various  silicated  rocks,  and 
especially  of  the  less  abundant,  and,  as  it  were,  exceptional  species 
just  mentioned.  The  first  of  these  supposes  that  the  minerals  of 
which  they  are  composed,  have  resulted  from  an  alteration  of  pre- 
viously existing  minerals,  often  very  unlike  in  composition  to  the 
present,  by  the  taking  away  of  certain  elements  and  the  addition 
of  certain  others.  This  is  the  theory  of  metamorphism  by  pseu- 
domorphic  changes,  as  they  are  called,  and  is  the  one  taught  b}^ 
the  now  reigning  school  of  chemical  geologists,  of  which  the 
learned  and  laborious  Bischof,  whose  recent  death  science  deplores, 
may  be  regarded  as  the  great  exponent.  The  second  hypothesis 
supposes  that  the  elements  of  these  various  rocks  were  originally 
deposited  as,  for  the  most  part,  chemically  formed  sediments,  or 
precipitates  ;  and  that  the  subsequent  changes  have  been  simply 

Quar.  Jour.  Geol.  Soc.,  xv,  489;  also,  Amer.  Jour.  Sci.,  II,  xxx,  133. 


ORIGIN   OF   CRYSTALLINE   ROCKS.  41 

molecular,  or,  at  most,  confined  in  certain  cases  to  reactions  be- 
tween the  mingled  elements  of  the  sediments,  with  the  elimination 
of  water  and  carbonic  acid.  It  is  proposed  to  consider  briefly, 
these  two  opposite  theories,  which  seek  to  explain  the  origin  of 
the  rocks  in  question  respectively  by  pseudomorphic  changes  in 
preexisting  crystalline  rocks,  and  by  the  crystallization  of  aqueous 
sediments,  for  the  most  part  chemically  formed  precipitates. 

Mineral  pseudomorphism,  that  is  to  say,  the  assumption  by  one 
mineral  substance  of  the  crystalline  form  of  another,  may  arise  in 
several  ways.  First  of  these  is  the  filling  up  of  a  mould  left  by 
the  solution  or  decomposition  of  an  imbedded  crystal,  a  process 
which  sometimes  takes  place  in  mineral  veins,  where  the  processes 
of  solution  and  deposition  can  be  freely  carried  on.  Allied  to 
this,  is  the  mineralization  of  organic  remains,  where  carbonate 
of  lime  or  silica,  for  example,  fills  the  pores  of  wood.  When  sub- 
sequent decay  removes  the  woody  tissue,  the  vacant  spaces  may, 
in  their  turn,  be  filled  by  the  same  or  another  species.  *  In  the 
second  place,  we  may  consider  pseudomorphs  from  alteration, 
which  are  the  result  of  a  gradual  change  in  the  composition  of  a 
mineral  species.  This  process  is  exemplified  in  the  conversion  of 
feldspar  into  kaolin  by  the  loss  of  its  alkali  and  a  portion  of  sil- 
ica, and  the  fixation  of  water,  or  in  the  change  of  chalybite  into 
limonite  by  the  loss  of  carbonic  acid  and  the  absorption  of  water 
and  oxygen. 

The  doctrine  of  pseudomorphism  by  alteration  as  taught  by  Gus- 
taf  Rose,  Haidinger,  Blum,  Volger,  Rammelsberg,  Dana,  Bischof, 
and  many  others,  leads  them,  however,  to  admit  still  greater  and 
more  remarkable  changes  than  these,  and  to  maintain  the  possi- 
bility of  converting  almost  any  silicate  into  any  other.  Thus,  by 
referring  to  the  pages  of  Bischof's  Lehrbuch  der  Geognosie,  it  will 
be  found  that  serpentine  is  said  to  exist  as  a  pseudomorph  after  au- 
gite,  hornblende,  olivine,  chondrodite,  .garnet,  mica,  and  probably 
also  after  labradorite,  and  even  orthoclase.  Serpentine  rock  or  oph- 
iolite  is  supposed  to  have  resulted,  in  different  cases,  from  the  al- 
teration of  hornblende-rock,  diorite,  granulite  and  even  granite. 
Not  only  silicates  of  protoxyds  and  aluminous  silicates  are  con- 
ceived to  be  capable  of  this  transformation,  but  probably  also 
quartz  itself ;  at  least,  Blum  asserts  that  meerschaum,  a  closely  re- 

*  Hunt  on  the  Silicification  of  Fossils,  Canadian  Naturalist,  new  series,  I,  46. 


42  ADDRESS    OF    T.    STERRY    HUNT. 

lated  silicate  of  magnesia,  which  sometimes  accompanies  serpen- 
tine, results  from  the  alteration  of  flint ;  while  according  to  Rose, 
serpentine  may  even  be  produced  from  dolomite,  which  we  are 
told  is  itself  produced  by  the  alteration  of  limestone.  But  this  is 
not  all,  —  feldspar  may  replace  carbonate  of  lime,  and  carbonate 
of  lime,  feldspar,  so  that,  according  to  Volger,  some  gneissoid  lime- 
stones are  probably  formed  from  gneiss  by  the  substitution  of 
calcite  for  orthoclase.  In  this  way,  we  are  led  from  gneiss  or 
granite  to  limestone,  from  limestone  to  dolomite,  and  from  dolo- 
mite to  serpentine,  or  more  directly  from  granite,  granulite  or 
diorite  to  serpentine  at  once,  without  passing  through  the  inter- 
mediate stages  of  limestone  and  dolomite,  till  we  are  ready  to 
exclaim  in  the  words  of  Goethe  :  — 

"  Mich  angstigt  das  Verfangliche 
Im  widrigen  Geschwatz, 
Wo  Nichts  verharret,  Alles  flieht. 
Wo  schon  verschwunden  was  man  sieht,"* 

which  we  may  thus  translate  :  — "I  am  vexed  with  the  sophistry  in 
their  contrary  jargon,  where  nothing  endures,  but  all  is  fugitive, 
and  where  what  we  see  has  already  passed  away." 

By  far  the  greater  number  of  cases  on  which  this  general  theory 
of  pseudomorphism  by  a  slow  process  of  alteration  in  minerals,  has 
been  based  are,  as  I  shall  endeavor  to  show,  examples  of  the  phe- 
nomenon of  mineral  envelopment,  so  well  studied  by  Delesse  in 
his  essay  on  Pseudomorphs,t  and  may  be  considered  under  two 
heads: — first,  that  of  symmetrical  envelopment,  in  which  one 
mineral  species  is  so  enclosed  within  the  other  that  the  two  appear 
to  form  a  single  crystalline  individual.  Examples  of  this  are  seen 
when  prisms  of  cyanite  are  surrounded  by  staurolite,  or  staurolite 
crystals  completely  enveloped  in  those  of  cyanite,  the  vertical  axes 
of  the  two  prisms  corresponding.  Similar  cases  are  seen  in  the 
enclosure  of  a  prism  of  red  in  an  envelope  of  green  tourmaline,  of 
allanite  in  epidote,  and  of  various  minerals  of  the  pyroxene  group 
in  one  another.  The  occurrence  of  muscovite  in  lepidolite,  and 
of  margarodite  in  lepidomelane,  or  the  inverse,  are  well-known 
examples,  and,  according  to  Scheerer,  the  crystallization  of  serpen- 
tine around  a  nucleus  of  olivine  is  a  similar  case.  This  phenome- 
non of  symmetrical  envelopment,  as  remarked  by  Delesse,  shows 

•  *Chinesisch-Deutsche  Jahres  und  Tages  Zeiten,  xi. 

t  Annales  des  Mines,  V,  xvi,  317-392. 


ORIGIN   OF   CRYSTALLINE   ROCKS.  43 

itself  with  species  which  are  generally  isomorphous  or  homceomor- 
phous,  and  of  related  chemical  composition.  Allied  to  this  is  the 
repeated  alternation  of  crystalline  laminae  of  related  species,  as 
in  perthite,  the  crystalline  cleavable  masses  of  which  consist  of 
thin,  alternating  layers  of  orthoclase  and  albite. 

Very  unlike  to  the  above  are  those  cases  of  envelopment  in 
which  no  relations  of  crystalline  symmetry  nor  of  similar  chemi- 
cal constitution  can  be  traced.  Examples  of  this  kind  are  seen  in 
garnet  crystals,  the  walls  of  which  are  shells,  sometimes  no 
thicker  than  paper,  enclosing  in  different  cases,  crystalline  carbon- 
ate of  lime,  epidote,  chlorite  or  quartz.  In  like  manner,  c^stal- 
line  shells  of  leucite  enclose  feldspar,  hollow  prisms  of  tourmaline 
are  filled  with  crystals  of  mica  or  with  hydrous  peroxyd  of  iron, 
and  crystals  of  beryl  with  a  granular  mixture  of  orthoclase  and 
quartz,  holding  small  crystals  of  garnet  and  tourmaline,  a  compo- 
sition identical  with  the  enclosing  granitic  veinstone.  *  Similar 
shells  of  galenite  and  of  zircon,  having  the  external  forms  of 
these  species,  are  also  found  filled  with  calcite.  In  many  of  these 
cases  the  process  seems  to  have  been  first  the  formation  of  a  hol- 
low mould  or  skeleton-crystal  (a  phenomenon  sometimes  observed 
in  salts  crystallizing  from  solutions) ,  the  cavity  being  subsequently 
filled  with  other  matters.  Such  a  process  is  conceivable  in  free 
crystals  found  in  veins,  as  for  example,  galenite,  zircon,  tourmaline, 
beryl  and  some  examples  of  garnet,  but  is  not  so  intelligible  in  the 
case  of  those  garnets  imbedded  in  mica-schist,  studied  by  Delesse, 
which  enclosed  within  their  crystalline  shells  irregular  masses  of 
white  quartz,  with  some  little  admixture  of  garnet.  Delesse  con- 
ceives these  and  similar  cases  to  be  produced  by  a  process  analogous 
to  that  seen  in  the  crystallization  of  calcite  in  the  Fontainebleau 
sandstone  ;  where  the  quartz  grains,  mechanically  enclosed  in  well- 
defined  rhombohedral  crystals,  equal,  according  to  him,  sixty-five 
per  cent.,  of  the  mass.  Very  similar  to  these  are  the  crystalloids 
with  the  form  of  orthoclase,  which  sometimes  consist  in  large  part 
of  a  granular  mixture  of  quartz,  mica  and  orthoclase,  with  a  little 
cassiterite,  and  in  other  cases,  contain  two-thirds  their  weight  of 
the  latter  mineral,  with  an  admixture  of  orthoclase  and  quartz. 
Crystals  with  the  form  of  scapolite,  but  made  up,  in  a  great  part,  of 
mica,  seem  to  be  like  cases  of  envelopment,  in  which  a  small  pro- 
portion of  one  substance  in  the  act  of  crystallization,  compels  in- 

*  Report  Geol.  Survey  of  Canada,  I860,  page  189. 


44  ADDRESS    OF   T.    STERRY   HUNT. 

to  its  own  crystalline  form  a  large  portion  of  some  foreign  material, 
which  may  even  so  mask  the  crystallizing  element  that  this  be- 
comes overlooked,  as  of  secondary  importance.  The  substance 
which,  under  the  name  of  houghite,  has  been  described  as  an  al- 
tered spinel,  is  found  by  analysis  to  be  an  admixture  of  vollknerite 
with  a  variable  proportion  of  spinel,  which,  in  some  specimens,  does 
not  exceed  eight  per  cent.,  but  to  which,  nevertheless,  these  crystal- 
loids appear  to  owe  their  more  or  less  complete  octohedral  form.  * 
The  above  characteristic  examples  of  symmetrical  and  asymmet- 
rical envelopment  are  cited  from  a  great  number  of  others  which 
might  have  been  mentioned.  Very  many  of  these  are  by  the  pseu- 
domorphists  regarded  as  results  of  partial  alteration.  Thus,  in 
the  case  of  associated  crystals  of  andalusite  and  cyanite,  Bischof 
does  not  hesitate  to  maintain  the  derivation  of  andalusite  from 
the  latter  species  by  an  elimination  of  quartz  ;  more  than  this,  as 
the  andalusite  in  question  occurs  in  a  granite-like  rock,  he  sug- 
gests that  itself  is  a  product  of  the  alteration  of  orthoclase.  In 
like  manner  the  mica,  which  in  some  cases  coats  tourmaline,  and 
in  others,  fills  hollow  prisms  of  this  mineral,  is  supposed  to  result 
from  a  subsequent  alteration  of  crystallized  tourmaline.  So  in 
the  case*  of  shells  of  leucite  filled  with  feldspar,  or  of  garnet  en- 
closing epidote,  or  chlorite,  or  quartz,  a  similar  transformation  of 
the  interior  is  supposed  to  have  been  mysteriously  effected,  while 
the  external  portion  of  the  crystal  remains  intact.  Again  the  ag- 
gregates of  tinstone,  quartz  and  orthoclase  having  the  form  of  the 
latter,  are,  by  Bischof  and  his  school,  looked  upon  as  results  of  a 
partial  alteration  of  previously  formed  orthoclase  crystals.  It 
needed  only  to  extend  this  view  to  the  crystals  of  calcite  enclos- 
ing sand-grains,  and  regard  these  as  the  result  of  a  partial  alter- 
ation of  the  carbonate  of  lime.  There  is  absolutely  no  proof 
that  these  hard  crystalline  substances  can  undergo  the  changes 
supposed,  or  can  be  absorbed  and  modified  like  the  tissues  of  a 
living  organism.  It  may,  moreover,  be  confidently  affirmed  that 
the  obvious  facts  of  envelopment  are  adequate  to  explain  all  the 
cases  of  association  upon  which  this  hypothesis  of  pseudomorphism 
by  alteration,  has  been  based.  Why  the  change  should  extend  to 
some  parts  of  a  crystal  and  not  to  others,  why  in  some  cases  the 
exterior  of  the  crystal  is  altered,  while  in  others  the  centre  alone 

*  Report  Geol.  Survey  of  Canada,  1866,  pp.  189, 213.    Amer.  Jour.  Sci.,  Ill,  i,  188. 


ORIGIN   OF    CRYSTALLINE   ROCKS.  45 

is  removed  and  replaced  by  a  different  material,  are  questions 
which  the  advocates  of  this  fanciful  hypothesis  have  not  explained. 
As  taught  by  Blum  and  Bischof,  however,  these  views  of  the  al- 
teration of  mineral  species  have  not  only  been  generally  accepted 
but  have  formed  the  basis  of  the  generally  received  theory  of  rock- 
metamorphism. 

Protests  against  the  views  of  this  school  have,  however,  not  been 
wanting.  Scheerer,  in  1846,  in  his  researches  in  Polymeric  Iso- 
morphism,* attempted  to  show  that  iolite  and  aspasiolite,  a  hy- 
drous species  which  had  been  looked  upon  as  resulting  from  its  al- 
teration, were  isomorphous  species  crystallizing  together,  and,  in 
like  manner,  that  the  association  of  olivine  and  serpentine  in  the 
same  crystal,  at  Snarum  in  Norway,  was  a  case  of  envelopment  of 
two  isomorphous  species.  In  both  of  these  instances  he  main- 
tained the  existence  of  isomorphous  relations  between  silicates  in 
which  3HO  replaced  MgO.  He  hence  rejected  the  view  of  Gustaf 
Rose  that  these  serpentine  crystals  were  results  of  the  alteration 
of  olivine,  and  supported  his  own  by  reasons  drawn  from  the  con- 
ditions in  which  the  crystals  occur.  In  1853  I  took  up  this  ques- 
tion and  endeavored  to  show  that  these  cases  of  isomorphism 
described  by  Scheerer,  entered  into  a  more  general  law  of*  isomor- 
phism pointed  out  by  me  among  homologous  compounds  differing 
in  their  formulas  by  wM2O2  (M  =  hydrogen  or  a  metal).  I  in- 
sisted, moreover,  on  its  bearing  upon  the  received  views  of  the 
alteration  of  minerals,  and  remarked,  "The  generally  admitted  no- 
tions of  pseudomorphism  seem  to  have  originated  in  a  too  exclu- 
sive plutonism,  and  require  such  varied  hypotheses  to  explain  the 
different  cases,  that  we  are  led  to  seek  for  some  more  simple  ex- 
planation and  to  find  it,  in  many  instances,  in  the  association  and 
crystallizing  together  of  homologous  and  isomorphous  species."! 
Subsequently,  in  1860,  I  combated  the  view  of  Bischof,  adopted 
by  Dana,  that  "  regional  metamorphism  is  pseudomorphism  on  a 
grand  scale,"  in  the  following  terms  :  — 

"  The  ingenious  speculations  of  Bischof  and  others,  on  the  pos- 
sible alteration  of  mineral  species  by  the  action  of  various  saline 
and  alkaline  solutions,  may  pass  for  what  they  are  worth,  although 
we  are  satisfied  that  \)y  far  the  greater  part  of  the  so-called  cases 
of  pseudomorphism  in  silicates  are  purely  imaginary,  and,  when 

*Pogg.  Annal.,  Ixviii,  319. 
tPogg.  Annal.,  Ixviii,  319. 


46  ADDRESS    OF   T.    STERRY  HUNT. 

real,  are  but  local  and  accidental  phenomena.  Bischofs  notion 
of  the  pseudomorphism  of  silicates  like  feldspars  and  pyroxenes, 
presupposes  the  existence  of  crystalline  rocks,  whose  generation 
this  neptunist  never  attempts  to  explain,  but  takes  his  starting- 
point  from  a  plutonic  basis." 

I  then  asserted  that  the  problem  to  be  solved  in  regional  meta- 
morphism  is  the  conversion  of  sedimentary  strata,  "derived  by 
chemical  and  mechanical  agencies  from  the  ocean-waters  and  pre- 
existing crystalline  rocks  into  aggregations  of  crystalline  silicates. 
These  metamorphic  rocks,  once  formed,  are  liable  to  alteration 
only  by  local  and  superficial  agencies,  and  are  not,  like  the  tissues 
of  a  living  organism,  subject  to  incessant  transformations,  the 
pseudomorphism  of  Bischof."  * 

I  had  not,  at  that  time,  seen  the  essay  by  Delesse  on  Pseudo- 
morphs  already  referred  to,  published  in  1859,  in  which  he  main- 
tained views  similar  to  those  set  forth  by  me  in  1853  and  1860, 
declaring  that  much  of  what  had  been  regarded  as  pseudomor- 
phism had  no  other  basis  than  the  observed  associations  of  miner- 
als, and  that  often  "  the  so-called  metamorphism  finds  its  natural 
explanation  in  envelopment."  These  views  he  ably  and  ingeni- 
ously defended  by  a  careful  discussion  of  the  whole  range  of  facts 
belonging  to  the  history  of  the  subject. 

My  own  expression  of  opinion  on  this  question,  in  1853,  had 
been  privately  criticised,  and  I  had  been  charged  with  a  want  of 
comprehension  of  the  question.  It  was,  therefore,  with  no  small 
pleasure,  that  I  not  only  saw  my  views  so  ably  supported  by 
Delesse,  but  read  the  language  of  Carl  Friedrich  Naumann,  who 
in  1861  wrote  to  Delesse  as  follows,  referring  to  his  essay  just 
noticed :  — 

"You  have  rendered  a  veritable  service  to  science  in  restricting 
pseudomorphs  to  their  true  limits,  and  separating  what  had  been 
erroneously  united  to  them.  As  you  have  remarked,  envelop- 
ments have,  for  the  most  part,  nothing  in  common  with  pseudo- 
morphs, and  it  is  inconceivable  that  they  have  been  united  by  so 
many  mineralogists  and  geologists.  It  appears  to  me,  moreover, 
that  they  commit  an  analogous  error,  when  they  regard  gneisses, 
amphibolites,  etc.,  as  being,  all.  of  them,  the  results  of  metamor- 
phic epigenesis,  and  not  original  rocks.  It  is  precisely  because 
pseudomorphism  has  been  so  often  confounded  with  metamorphism 
that  this  error  has  found  acceptance.  I  only  admit  a  pseudomorph 

*  Amer.  Jouv.  Sci.,  II,  xxx,  135. 


ORIGIN   OF    CRYSTALLINE   ROCKS.  47 

where  there  is  some  crystal  the  form  of  which  has  been  preserved. 
There  are  very  many  metamorphic  substances  which  are,  in  no  sense 
of  the  word,  pseudomorphs.  Had  the  name  of  crystalloid  been 
chosen,  instead  of  pseudomorph,  this  confusion  would  certainly 
have  never  found  its  way  into  the  science.  I  think,  with  you,  that 
the  envelopment  of  two  minerals  is  most  generally  explained  by 
a  contemporaneous  and  original  crystallization.  Secondary  envel- 
opments, however,  exist,  and  such  may  be  called  pseudomorphs 
or  crystalloids,  if  they  reproduce  exactly  the  form  of  the  crystal 
enveloped,  whether  this  last  still  remains,  or  has  entirely  disap- 
peared."* 

It  is  unnecessary  to  remark  that  the  view  of  Delesse  and  Nau- 
mann,  viz. :  that  the  so-called  cases  of  pseudomorphism,  on  which 
the  theory  of  metamorphism  by  alteration  has  been  built,  are, 
for  the  most  part,  examples  of  association  and  envelopment,  and 
the  result  of  a  contemporaneous  and  original  crystallization,  —  is 
identical  with  the  view  suggested  by  Scheerer,  and  generalized  by 
myself  long  before,  when,  in  1853,  I  sought  to  explain  the  phe- 
nomena in  question  by  "the  association  and  crystallizing  together 
of  homologous  and  isomorphous  species." 

Later,  in  1862,  I  wrote  as  follows  :  — 

"Pseudomorphism,  which  is  the  change  of  one  mineral  species 
into  another,  by  the  introduction  or  the  elimination  of  some  ele- 
ment or  elements,  presupposes  metamorphism  (i.  e.,  metamorphic 
or  crystalline  rocks),  since  only  definite  mineral  species  can  be  the 
subjects  of  this  process.  To  confound  metamorphism  with  pseu- 
domorphism, as  Bischof,  and  others  after  him  have  done,  is  there- 
fore an  error.  It  may  be  farther  remarked,  that,  although  certain 
pseudomorphic  changes  may  take  place  in  some  mineral  species, 
in  veins  and  near  the  surface,  the  alteration  of  great  masses  of 
silicated  rocks  by  such  a  process  is  as  yet  an  unproved  hypoth- 
esis."! 

Thus  this  unproved  theory  of  pseudomorphism,  as  taught  by 
Bischof,  does  not,  even  if  admitted  to  its  fullest  extent,  advance 
us  a  single  step  towards  a  solution  of  the  problem  of  the  origin 
of  the  various  silicates,  which,  singly  or  intermingled,  make  up 
beds  in  the  crystalline  schists.  Granting,  for  the  sake  of  argu- 
ment, that  serpentine  results  from  the  alteration  of  olivine  or 
labradorite,  and  steatite  or  chlorite  from  hornblende,  the  origin  of 

*Bull.  Soc.  Geol.  de  France,  II,  xviii,  678. 

t  Descriptive  Catalogue.  Crystalline  Rocks  of  Canada,  p.  80,  London  Exhibition,  1862 ; 
also.  Dublin  Quar.  Journal,  July  1863,  and  Amer.  Jour.  Sci.,  II,  xxxvi,  218. 


48  ADDRESS   OP   T.    STERRY   HUNT. 

these  anhydrous  silicates,  which  are  the  subjects  of  the  supposed 
change,  is  still  unaccounted  for.  The  explanation  of  this  short- 
sightedness is  not  far  to  seek ;  as  already  remarked,  Bischof, 
although  a  professed  neptimist,  starts  from  a  plutonic  basis. 
When  the  epigenic  origin  of  serpentine  and  its  related  rocks  was 
first  taught,  these  were  regarded  as  eruptive  and  unstratified,  and 
it  was  easy  to  imagine  intruded  masses  of  dioritic  and  feldspathic 
rocks,  which  had  become  the  subjects  of  alteration.  As,  however, 
the  progress  of  careful  investigation  in  the  field  has  shown  the 
stratified  character  of  these  serpentines,  diallage-rocks,  steatites, 
etc.,  and  their  intercalation  among  limestones,  argillites,  quartz- 
ites,  gneisses,  and  mica-schists,  and  even  among  feldspathic  and 
hornblendic  strata,  we  are  forced  to  reject,  with  Naumann,  the 
notion  of  their  epigenic  derivation,  and  to  regard  them  as  original 
rocks. 

This  view  brings  us  face  to  face  with  the  problem  of  metamor- 
phism  as  defined  by  me  in  1860  *  (ante,  page  46).  We  must  either 
admit  that  these  crystalline  schists  were  created  as  we  find  them, 
or  suppose  that  they  were  once  sands,  clays,  marls,  etc. ;  in 
a  word,  sediments  of  chemical  and  mechanical  origin,  which 
by  a  subsequent  process  have  been  consolidated  and  crystallized. 
Whence,  then,  come  these  silicates  of  magnesia,  lime,  and  iron, 
which  are  the  sources  of  serpentine,  hornblende,  steatite,  chlorite, 
etc.  ?  This  is  the  question  which  I  proposed  in  that  same  year, 
when,  after  discussing  the  results  of  my  examinations  of  the  ter- 
tiary rocks  near  Paris,  containing  layers  of  a  hydrous  silicate  of 
magnesia  related  to  talc  in  composition,  among  unaltered  lime- 
stones and  clays,  I  remarked  that  it  is  evident  "  such  silicates 
may  be  formed  in  basins  at  the  earth's  surface,  by  reactions 
between  magnesian  solutions  and  dissolved  silica;"  and,  after 
some  farther  discussion,  said  "farther  inquiries  in  this  direc- 
tion may  show  to  what  extent  certain  rocks  composed  of  calca- 
reous and  magnesian  silicates  may  be  directly  formed  in  the 
moist  way."f  Subsequently,  in  a  paper  on  "The  Origin  of 
some  Magnesian  and  Aluminous  Rocks,"  printed  in  the  Cana- 
dian Naturalist  for  June,  1860,  J  I  repeated  these  considerations, 
referring  to  the  well-known  fact  that  silicates  of  lime,  magnesia 

*Amer.  Jour.  Sci.,  II,  xxx,  135. 
flbid.,  II,  xxix,  284;  also  II,  xl,  49. 
J  Ibid.,  II,  xxxii,  286. 


ORIGIN   OF   CRYSTALLINE   ROCKS.  49 

and  iron-oxyd  are  deposited  during  the  evaporation  of  natural 
waters,  including  those  of  alkaline  springs  and  of  the  Ottawa 
River.  Having  described  the  mode  of  occurrence  of  the  mag- 
nesian  silicate,  sepiolite,  in  the  Paris  basin,  and  the  related 
quincite,  containing  some  iron-oxyd  and  disseminated  in  lime- 
stone, I  suggested  that  while  steatite  has  been  derived  from  a 
compound  like  sepiolite,  the  source  of  serpentine  was  to  be  sought 
in  another  silicate  richer  in  magnesia ;  and,  moreover,  that  chlo- 
rite, unless  the  result  of  a  subsequent  reaction  between  clay  and 
carbonate  of  magnesia,  was  directly  formed  by  a  process  analogous 
to  that  which  (according  to  Scheerer)  has,  in  recent  times,  caused 
the  deposition  from  waters  of  neolite,  a  hydrous  alumino-magne- 
sian  silicate  approaching  to  chlorite  in  composition,*  "the  type  of 
a  reaction  which  formerly  generated  beds  of  chlorite  in  the  same 
way  as  those  of  sepiolite  or  talc."  Delesse,  subsequently,  in  1861, 
in  his  essay  on  Rock-Metamorphism  insisted  upon  the  sepio- 
lites  or  so-called  magnesian  marls,  as  probably  the  source  of 
steatite,  and  suggested  the  derivation  of  serpentine,  chlorite,  and 
other  related  minerals  of  the  crystalline  schists,  from  deposits 
approaching  these  marls  in  composition.f  He  recalled,  also,  the 
occurrence  of  chromic  oxyd,  a  frequent  accompaniment  of  these 
magnesian  minerals,  in  the  hydrated  iron  ores  of  the  same  geo- 
logical horizon  with  the  magnesian  marls  in  France.  Delesse  did 
not,  however,  attempt  to  account  for  the  origin  of  these  deposits 
of  magnesian  marls,  in  explanation  of  which  I  afterwards  verified 
Bischof  s  observations  on  the  sparing  solubility  of  silicate  of 
magnesia,  and  showed  that  silicate  of  soda,  or  even  artificial  hy- 
drated silicate  of  lime,  when  added  to  waters  containing  magne- 
sian chlorid  or  sulphate,  gives  rise,  by  double  decomposition,  to  a 
very  insoluble  magnesian  silicate.  J 

To  explain  the  generation  of  silicates  like  labradorite,  scapo- 
lite,  garnet,  and  saussurite,  I  suggested  that  double  aluminous 
silicates  allied  to  the  zeolites  might  have  been  formed,  and  subse- 
quently rendered  anhydrous.  The  production  of  zeolitic  minerals 
observed  by  Daubree  at  Plombieres  and  Luxeuil  by  the  action  of 
a  silicated  alkaline  water  on  the  masonry  of  ancient  Roman  baths, 
was  appealed  to  by  way  of  illustration.  It  had  there  been  shown 

*  Pogg.  Anna!.,  Ixxi,  288. 

t  Etudes  sur  le  Metamorphisme,  quarto,  pp.  91.    Paris,  1861. 

J  Amer.  Jour.  Sci.,  H,  xl,  49. 

AMER.   NAT.,    ASSOC.    NUMBER.  4 


50  ADDRESS    OF   T.    STEERY   HUNT. 

by  Daubree  that  the  elements  of  the  zeolites  had  been  derived  in 
part  from  the  waters,  and  in  part  from  the  mortar  and  even  the 
clay  of  the  bricks,  which  had  been  attacked,  and  had  entered  into 
combination  with  the  soluble  matters  of  the  water  to  form  chaba- 
zite.  I,  however,  at  the  same  time  pointed  out  another  source  of 
silicated  minerals,  upon  which  I  had  insisted  since  1857,  viz. : 
the  reaction  between  silicious  or  argillaceous  matters  and  earthy 
carbonates  in  the  presence  of  alkaline  solutions.  Numerous  ex- 
periments showed  that  when  solutions  of  an  alkaline  carbonate 
were  heated  with  a  mixture  of  silica  and  carbonate  of  magnesia, 
the  alkaline  silicate  formed  acted  upon  the  latter,  yielding  a  sili- 
cate of  magnesia,  and  regenerating  the  alkaline  carbonate ;  which, 
without  entering  into  permanent  combination,  was  the  medium 
through  which  the  union  of  the  silica  and  the  magnesia  was  ef- 
fected. In  this  way  I  endeavored  to  explain  the  alteration,  in  the 
vicinity  of  a  great  intrusive  mass  of  dolerite,  of  a  gray  Silurian 
limestone,  which  contained,  besides  a  little  carbonate  of  magne- 
sia and  iron-oxyd,  a  portion  of  very  silicious  matter,  consisting 
apparently  of  comminuted  orthoclase  and  quartz.  In  place  of 
this,  there  had  been  developed  in  the  limestone,  near  its  contact 
with  the  dolerite,  an  amorphous  greenish  basic  silicate,  which  had 
seemingly  resulted  from  the  union  of  the  silica  and  alumina  with 
the  iron-oxyd,  the  magnesia  and  a  portion  of  lime.  By  the  crys- 
tallization of  the  products  thus  generated  it  was  conceived  that 
minerals  like  hornblende,  garnet  and  epidote  might  be  developed 
in  earthy  sediments,  and  many  cases  of  local  alteration  explained. 
Inasmuch  as  the  reaction  described  required  the  intervention  of 
alkaline  solutions,  rocks  from  which  these  were  excluded  would 
escape  change,  although  the  other  conditions  might  not  be  want- 
ing. The  natural  associations  of  minerals,  moreover,  led  me  to 
suggest  that  alkaline  solutions  might  favor  the  crystallization  of 
aluminous  silicates,  and  thus  convert  mechanical  sediments  into 
gneisses  and  mica-schists.  The  ingenious  experiments  of  Dau- 
bree on  the  part  which,  solutions  of  alkaline  silicates,  at  elevated 
temperatures,  may  play  in  the  formation  of  crystallized  minerals, 
such  as  feldspar  and  pyroxene,  were  posterior  to  my  early  publi- 
cations on  the  subject,  and  fully  justified  the  importance  which, 
early  in  1857, 1  attributed  to  the  intervention  of  alkaline  silicates 
in  the  formation  of  crystalline  silicated  minerals.  * 
*Proc.  Royal  Soc.,  May  7, 1857.  Amer,  Jour,  Sci.,  II,  xxiii,  438,  and  xxv,  289  and  435. 


ORIGIN   OF   CRYSTALLINE   ROCKS.  51 

While,  however,  there  is  good  reason  to  believe  that  solutions  of 
alkaline  silicates  or  carbonates  have  been  efficient  agents  in  the 
crystallization  and  molecular  re-arrangement  of  ancient  sediments, 
and  have  also  played  an  important  part  in  that  local  alteration  of 
sedimentary  strata  which  is  often  observed  in  the  vicinity  of  intru- 
sive rocks,  it  is  clear  to  me  that  the  agency  of  these  solutions  is 
less  universal  than  once  supposed  by  Daubree  and  myself,  and  will 
not  account  for  the  formation  of  various  silicated  rocks  found 
among  crystalline  schists,  such  as  serpentine,  hornblende,  steatite 
and  chlorite.  When  I  commenced  the  study  of  these  crystalline 
strata  I  was  led,  in  accordance  with  the  almost  universally  received 
opinion  of  geologists,  to  regard  them  as  resulting  from  a  subse- 
quent alteration  of  paleozoic  sediments,  which,  according  to  differ- 
ent authorities,  were  of  Cambrian,  Silurian  or  Devonian  age.  Thus 
in  the  Appalachian  region,  as  we  have  already  seen,  they  have,  on 
supposed  stratigraphical  evidence,  been  successively  placed  at  the 
base,  at  the  summit,  and  in  the  middle  of  the  Lower  Silurian  or 
Champlain  division  of  the  New  York  system.  A  careful  chemical 
examination  among  the  unaltered  paleozoic  sediments,  which  in 
Canada  were  looked  upon  as  the  stratigraphical  equivalents  of  the 
bands  of  magnesian  silicates  in  these  crystalline  schists,  showed 
me,  however,  no  magnesian  rocks  except  certain  silicious  and 
ferruginous  dolomites.  From  a  consideration  of  reactions  which 
I  had  observed  to  take  place  in  such  admixtures  in  presence  of 
heated  alkaline  solutions,  and  from  the  composition  of  the  basic 
silicates  which  I  had  found  to  be  formed  in  silicious  limestones 
near  their  contact  with  eruptive  rocks,  I  was  led  to  suppose  that 
similar  actions,  on  a  grand  scale,  might  transform  these  silicious 
dolomites  of  the  unaltered  strata  into  crystalline  magnesian  sili- 
cates. 

Farther  researches,  however,  convinced  me  that  this  view  was 
inapplicable  to  the  crystalline  schists  of  the  Appalachians,  since, 
apart  from  the  geognostical  considerations  set  forth  in  the  previous 
part  of  this  paper,  I  found  that  these  same  crystalline  strata  hold 
beds  of  quartzose  dolomite  and  magnesian  carbonate,  associated  in 
such  intimate  relations  with  beds  of  serpentine,  diallage  and  stea- 
tite, as  to  forbid  the  notion  that  these  silicates  could  have  been 
generated  by  any  transformations  or  chemical  re-arrangement  of 
mixtures  like  the  accompanying  beds  of  quartzose  magnesian  car- 
bonates. Hence  it  was  that  already,  in  1860,  as  shown  above,  I 


52  ADDRESS    OF   T.    STERRY   HUNT. 

announced  my  conclusion  that  serpentine,  chlorite  and  steatite  had 
been  derived  from  silicates  like  sepiolite,  directly  formed  in  waters 
at  the  earth's  surface,  and  that  the  crystalline  schists  had  resulted 
from  the  consolidation  of  previously  formed  sediments,  partly 
chemical  and  partly  mechanical  in  their  origin.  The  latter  being 
chiefly  silico-aluminous,  took,  in  part,  the  forms  of  gneiss  and  mica- 
schists,  while  from  the  more  argillaceous  strata,  poorer  in  alkali, 
much  of  the  aluminous  silicate  crystallized  as  andalusite,  stauro- 
lite,  cyanite  and  garnet.  These  views  were  reiterated  in  1863,* 
and  farther  in  1864,  in  the  following  language,  as  regards  the 
chemically-formed  sediments :  "  steatite,  serpentine,  pyroxene, 
hornblende,  and  in  many  cases,  garnet,  epidote  and  other  silicated 
minerals  are  formed  by  a  crystallization  and  molecular  re-arrange- 
ment of  silicates  generated  by  chemical  processes  in  waters  at  the 
earth's  surface."  |  Their  alteration  and  crj^stallization  was  com- 
pared to  that  of  the  mechanically  formed  feldspathic,  silicious  and 
argillaceous  sediments  just  mentioned. 

The  direct  formation  of  the  crystalline  schists  from  an  aqueous 
magma  is  a  notion  which  belongs  to  an  early  period  in  geological 
theory.  Delabeche  in  1834J  conceived  that  they  were  thrown 
down  as  chemical  deposits  from  the  waters  of  the  heated  ocean, 
after  its  reaction  on  the  crust  of  the  cooling  globe,  and  before  the 
appearance  of  organic  life.  This  view  was  revived  by  Daubree  in 
1860.  Having  sought  to  explain  the  alteration  of  paleozoic  strata 
of  mechanical  origin,  by  the  action  of  heated  waters,  he  proceeds 
to  discuss  the  origin  of  the  still  more  ancient  crystalline  schists. 
The  first  precipitated  waters,  according  to  him,  acting  on  the  anhy- 
drous silicates  of  the  earth's  crust,  at  a  very  elevated  temperature, 
and  at  a  great  pressure,  wrhich  he  estimated  at  two  hundred  and 
fifty  atmospheres,  formed  a  magma,  from  which,  as  it  cooled,  were 
successively  deposited  the  various  strata  of  the  crystalline  schists. § 
This  hypothesis,  violating,  as  it  does,  all  the  notions  which  sound 
theory  teaches  with  regard  to  the  chemistry  of  a  cooling  globe, 
has,  moreover,  to  encounter  grave  geognostical  difficulties.  The 
pre-Silurian  crystalline  rocks  belong  to  two  or  more  distinct  sys- 
tems of  different  ages,  succeeding  each  other  in  discordant  strat- 

*Geol.  of  Canada,  pp.  577—581. 

f  Amer.  Jour.  Sci.,  II,  xxxvii,  266,  and  xxxviii,  183. 

J  Researches  in  Theoretical  Geology,  pp.  297-300. 

§  Etudes  et  experiences  synthetiques  sur  le  Metamorphisme,  pp.  119-121. 


ORIGIN   OF   CRYSTALLINE   ROCKS.  53 

ification.  The  whole  history  of  these  rocks,  moreover,  shows  that 
their  various  alternating  strata  werl  deposited,  not  as  precipi- 
tates from  a  seething  solution,  but  under  conditions  of  sedimen- 
tation very  like  those  of  more  recent  times.  In  the  oldest  known 
of  them,  the  Laurentian  system,  great  limestone  formations  are 
interstratified  with  gneisses,  quartzites  and  even  with  conglom- 
erates. All  analogy,  moreover,  leads  us  to  conclude  that  even  at 
this  early  period,  life  existed  at  the  surface  of  the  planet.  Great 
accumulations  of  iron-oxyd,  beds  of  metallic  sulphids  and  of 
graphite,  exist  in  these  oldest  strata,  and  we  know  of  no  other 
agency  than  that  of  organic  matter,  capable  of  generating  these 
products. 

Bischof  had  already  arrived  at  the  conclusion,  which  in  the 
present  state  of  our  knowledge  seems  inevitable,  that  "  all  the  car- 
bon yet  known  to  occur  in  a  free  state,  can  only  be  regarded  as 
a  product  of  the  decomposition  of  carbonic  acid,  and  as  derived 
from  the  vegetable  kingdom."  He  farther  adds,  "living  plants 
decompose  carbonic  acid ;  dead  organic  matters  decompose  sul- 
phates, so  that,  like  carbon,  sulphur  appears  to  owe  its  existence 
in  a  free  state  to  the  organic  kingdom."*  As  a  decomposition 
(deoxidation)  of  sulphates  is  necessary  to  the  production  of  me- 
tallic sulphids,  the  presence  of  the  latter,  not  less  than  that  of 
free  sulphur  and  free  carbon,  depends  on  organic  bodies ;  the  part 
which  these  play  in  reducing  and  rendering  soluble  the  peroxyd  of 
iron,  and  in  the  production  of  iron  ores  is,  moreover,  well  known. 
It  was,  therefore,  that,  after  a  careful  study  of  these  ancient  rocks, 
I  declared  in  May,  1858,  that  a  great  mass  of  evidence  "points 
to  the  existence  of  organic  life,  even  during  the  Laurentian  or  so- 
called  azoic  period."  | 

This  prediction  was  soon  verified  in  the  discovery  of  the  Eozoon 
Canadense,  of  Dawson,  the  organic  character  of  which  is  now  ad- 
mitted by  all  zoologists  and  geologists  of  authority.  But  with 
this  discovery,  appeared  another  fact,  which  afforded  a  signal  veri- 
fication of  my  theory  as  to  the  origin  and  mode  of  deposition  of 
serpentine  and  pyroxene.  The  microscopic  and  chemical  re- 
searches of  Dawson  and  myself  showed  that  the  calcareous  skel- 
eton of  this  foraminiferal  organism  was  filled  with  the  one  or  the 
other  of  these  silicates  in  such  a  manner  as  to  make  it  evident  that 

*  Bischof,  Lehrbuch,  1st.  ed.,  II,  95.    English  ed.,  I,  252,  344. 
t  Amer.  Jour.  Science,  II,  xxv,  436. 


54  ADDRESS    OF   T.    STERRY   HUNT. 

they  had  replaced  the  sarcode  of  the  animal,  precisely  as  glauco- 
nite  and  similar  silicates  hare,  from  the  Silurian  time's  to  the  pres- 
ent, filled  and  injected  more  recent  foraminiferal  skeletons.  I  re- 
called, in  connection  with  this  discovery  the  observations  of 
Ehrenberg,  Mantell  and  Bailey,  and  the  more  recent  ones  of  Pour- 
tales,  to  the  effect  that  glauconite  or  some  similar  substance  occa- 
sionally fills  the  spines  of  Echini,  the  cavities  of  corals  and  mille- 
pores,  the  canals  in  the  shells  of  Balanus,  and  even  forms  casts 
of  the  holes  made  by  burrowing  sponges  (Clionia)  and  worms. 
The  significance,  of  these  facts  was  farther  illustrated  by  showing 
that  the  so-called  glauconites  differ  considerably  in  composition, 
some  of  them  containing  more  or  less  alumina  or  magnesia,  and 
one  from  the  tertiary  limestones  near  Paris  being,  according  to 
Berthier,  a  true  serpentine.  * 

These  facts  in  the  history  of  Eozoon,  were  first  made  known  by 
me  in  May,  1864,  in  the  American  Journal  of  Science,  and  subse- 
quently more  in  detail,  February,  1865,  in  a  communication  to  the 
Geological  Society  of  London,  f  They  were  speedily  verified  by 
Dr.  Gumbel,  who  was  then  engaged  in  the  study  of  the  ancient 
crystalline  schists  of  Bavaria,  and  soon  recognized  the  existence, 
in  the  limestones  of  the  old  Hercynian  gneiss,  of  the  characteris- 
tic Eozoon  Canadense,  injected  with  silicates  in  a  manner  precisely 
similar  to  that  observed  by  Dawson  and  myself.  J  Later,  in  1869, 
Robert  Hoffmann  described  the  results  of  a  minute  chemical  exam- 
ination of  the  Eozoon  from  Raspenau,  in  Bohemia,  confirming  the 
previous  observations  in  Canada  and  Bavaria.  He  showed  that 
the  calcareous  shell  of  the  Eozoon,  examined  by  him,  had  been  in- 
jected by  a  peculiar  silicate,  which  may  be  described  as  related  in 
composition  both  to  glauconite  and  to  chlorite.  The  masses  of 
Eozoon  he  found  to  be  enclosed  and  wrapped  around  by  thin  al- 
ternating layers  of  a  green  magnesian  silicate  allied  to  picrosmine, 
and  a  brown  non-magnesian  mineral,  which  proved  to  be  a  hy- 
drous silicate  of  alumina,  ferrous  oxyd  and  alkalies,  related  to 
fahlunite,  or  more  nearly  to  jollyte  in  composition.  § 

Still  more  recently,  in  the  course  of  the  present  year,  Dr.  Daw- 
son  detected  a  mineral  insoluble  in  acids,  injecting  the  pores  of 

*  Amer.  Jour.  Sci.,  II,  xl,  360,  Report  Geol.  Survey  Canada,  1866,  p.  231,  and  Quar. 
Geol.  Jour.,  XXI,  71. 

t  Amer.  Jour.  Sci.,  II,  xxxvii,  431.    Quar.  Geol.  Jour.,  XXI,  67. 
J  Proc.  Royal  Bavar.  Acad.  for  1866,  and  Can.  Naturalist,  new  series  III,  81. 
§  Jour.  fur.  Prakt.  Chem.,  May,  1869,  and  Amer.  Jour.  Sci.,  Ill,  i,  378. 


ORIGIN  OF  CRYSTALLINE   ROCKS.  55 

crinoidal  stems  and  plates  in  a  paleozoic  limestone  from  New 
Brunswick,  which  is  made  up  of  organic  remains.  This  silicate 
which,  in  decalcified  specimens,  shows  in  a  beautiful  manner  the 
intimate  structure  of  these  ancient  crinoids,  I  have  found  by  analy- 
sis to  be  a  hydrous  silicate  of  alumina  and  ferrous  oxyd,  with 
magnesia  and  alkalies,  closely  related  to  fahlunite  and  to  jollyte.* 
The  microscopic  examinations  of  Dr.  Dawson  show  that  this  sil- 
icate injected  the  pores  of  the  crinoidal  remains  and  some  of  the 
interstices  of  the  associated  shell-fragments,  before  the  introduc- 
tion of  the  calcite  which  cements  the  mass.  I  have  since  found  a 
silicate  almost  identical  with  this,  occurring  under  similar  condi- 
tions in  an  Upper  Silurian  limestone  said  to  be  from  Llangedoc  in 
Wales. 

Giimbel,  meanwhile,  in  the  essay  on  the  Laurentian  rocks  of  Ba- 
varia, in  1866,  already  referred  to,  fully  recognized  the  truth  of 
the  views  which  I  had  put  forward,  both  with  regard  to  mineralogy 
of  Eozoon  and  to  the  origin  of  the  crystalline  schists.  His  results 
are  still  farther  detailed  in  his  Geognost.  Beschreibung  des  ostbayeris- 
ches  Grenzegebirges,  1868,  p.  833.  Credner,  moreover,  as  he  tells 
us,  f  had  already  from  his  mineralogical  and  lithological  studies, 
been  led  to  admit  my  views  as  to  the  original  formation  of  serpen- 
tine, pyroxene  and  similar  silicates  (which  he  cites  from  my  paper 
of  1865,  above  referred'to  j),  when  he  found  that  Giimbel  had  ar- 
rived at  similar  conclusions.  The  views  of  the  latter,  as  cited  by 
Credner  from  the  work  just  referred  to,  are  in  substance  as  fol- 
lows: — The  crystalline  schists,  with  their  interstratified  layers, 
have  all  the  characters  of  altered  sedimentary  deposits,  and  from 
their  mode  of  occurrence  cannot  be  of  igneous  origin,  nor  the  result 
of  epigenic  action.  The  originally  formed  sediments  are  conceived 
to  have  been  amorphous,  and  under  moderate  heat  and  pressure  to 
have  arranged  themselves,  and  crystallized,  generating  various 
mineral  species  in  their  midst  by  a  change,  which,  to  distinguish  it 
from  metamorphism  by  an  epigenic  process,  Giimbel  happily  des- 
ignates diagenesis. 

It  is  unnecessary  to  remark,  that  these  views,  the  conclusions 
from  the  recent  studies  of  Giimbel  in  Germany  and  Credner  in 
North  America,  are  identical  with  those  put  forth  by  me  in  1860. 

*  Amer.  Jour.  Sci.,  III,  i,  379. 

t  Hermann  Credner;  die  Gleiderung  der  Eozoischen  Fonnationsgruppe  Xord  Amer- 
ikas.    Halle  1869.    J  That  in  the  Quar.  Geol.  Jour.,  TTXI,  67. 


56  ADDRESS    OF    T.    STERRY   HUNT. 

At  the  early  periods  in  which  the  materials  of  the  ancient  crys- 
talline schists  were  accumulated,  it  cannot  be  doubted  that  the 
chemical  processes  which  generated  silicates  were  much  more  ac- 
tive than  in  more  recent  times.  The  heat  of  the  earth's  crust 
was  probably  then  far  greater  than  at  present,  while  a  high  tem- 
perature prevailed  at  comparatively  small  depths,  and  thermal 
waters  abounded.  A  denser  atmosphere,  charged  with  carbonic 
acid  gas,  must  also  have  contributed  to  maintain,  at  the  earth's 
surface,  a  greater  degree  of  heat,  though  one  not  incompatible 
with  the  existence  of  organic  life.  *  These  conditions  must  have 
favored  many  chemical  processes,  which,  in  later  times,  have 
nearly  ceased  to  operate.  Hence  we  find  that  subsequently  to 
the  eozoic  times,  silicated  rocks  of  clearly  marked  chemical  ori- 
gin are  comparatively  rare.  In  the  mechanical  sediments  of  later 
periods  certain  crystalline  minerals  may  be  developed  by  a  process 
of  molecular  re-arrangement  —  diagenesis.  These  are,  in  the  feld- 
spathic  and  aluminous  sediments,  orthoclase,  muscovite,  garnet, 
staurolite,  cyanite  and  chiastolite,  and  in  the  more  basic  sedi- 
ments, hornblendic  minerals.  It  is  possible  that  these  latter  and 
similar  silicates  may  sometimes  be  generated  by  reactions  between 
silica  on  the  one  hand,  and  carbonates  and  oxyds,  on  the  other, 
as  already  pointed  out  in  some  cases  of  local  alteration.  Such  a 
case  may  apply  to  more  or  less  hornblendic  gneisses,  for  exampley 
but  no  sediments,  not  of  direct  chemical  origin,  are  pure  enough 
to  have  given  rise  to  the  great  beds  of  serpentine,  pyroxene,  stea- 
tite, labradorite,  etc.,  which  abound  in  the  ancient  crystalline 
schists.  Thus,  while  the  materials  for  producing,  by  diagenesis, 
the  aluminous  silicates  just  mentioned,  are  to  be  met  with  in  the 
mud  and  clay-rocks  of  all  ages,  the  chemically  formed  silicates, 
capable  of  crystallizing  into  pyroxene,  talc,  serpentine,  etc.,  have 
only  been  formed  under  special  conditions. 

The  same  reasoning  which  led  me  to  maintain  the  theory  of  an 
original  formation  of  the  mineral  silicates  of  the  crystalline  schists, 
induced  me  to  question  the  received  notion  of  the  epigenic  origin 
of  gypsums  and  magnesian  limestones  or  dolomites.  The  inter- 
stratification  of  dolomites  and  pure  limestones,  and  the  enclosure 
of  pebbles  of  the  latter  in  a  paste  of  crystalline  dolomite,  are  of 
themselves  sufficient  to  show  that  in  these  cases,  at  least,  dolo- 
mites have  not  been  formed  by  the  alteration  of  pure  limestones. 

*  Amer.  Jour.  Sci.,  II,  xxxvi,  396. 


ORIGIN    OF    CRYSTALLINE   ROCKS.  57 

The  first  results  of  a  very  long  series  of  experiments  and  inquiries 
into  the  history  of  gypsum,  were  published  by  me  in  1859,  and 
farther  researches,  reiterating  and  confirming  my  previous  conclu- 
sions, appeared  in  1866.*  In  these  two  papers,  it  will,  I  think,  be 
found  that  the  following  facts  in  the  history  of  dolomite  are  es- 
tablished, viz. :  first,  its  origin  in  nature  by  direct  sedimentation, 
and  not  by  the  alteration  of  non-magnesian  limestones ;  second, 
its  artificial  production  by  the  direct  union  of  carbonate  of  lime 
and  hydrous  carbonate  of  magnesia,  at  a  gentle  heat,  in  the  pres- 
ence of  water.  As  to  the  sources  of  the  hydrous  magnesian  car- 
bonate, I  have  endeavored  to  show  that  it  is  formed  from  the 
magnesian  chlorid  or  sulphate  of  the  sea  or  other  saline  waters  in 
two  ways  : — first,  by  the  action  of  the  bicarbonate  of  soda  found 
in  many  natural  waters  ;  this,  after  converting  all  soluble  lime-salts 
into  insoluble  carbonate,  forms  a  comparatively  soluble  bicarbon- 
ate of  magnesia,  from  which  a  hydrous  carbonate  slowly  separates  : 
second,  by  the  action  of  bicarbonate  of  lime  in  solution,  which, 
with  sulphate  of  magnesia  gives  rise  to  gj^sum  ;  this  first  crystal- 
lizes out,  leaving  behind  a  much  more  soluble  bicarbonate  of  mag- 
nesia, which  deposits  the  hydrous  carbonate  in  its  turn.  In  this 
waj-,  for  the  first  time,  in  1859,  the  origin  of  gypsums  and  their  in- 
timate relation  with  magnesian  limestones  were  explained. 

It  was,  moreover,  shown  that  to  the  perfect  operation  of  this  re- 
action, an  excess  of  carbonic  acid  in  the  solution,  during  the  evap- 
oration, was  necessary  to  prevent  the  decomposing  action  of  the 
hydrous  mono-carbonate  of  magnesia  upon  the  already  formed 
gypsum.  Having  found  that  a  prolonged  exposure  to  the  air,  by 
permitting  the  loss  of  carbonic  acid,  partially  interfered  with  the 
process,  I  was  led  to  repeat  the  experiment  in  a  confined  atmos- 
phere, charged  with  carbonic  acid,  but  rendered  drying  by  the 
presence  of  a  layer  of  dessicated  chlorid  of  calcium.  As  had 
been  foreseen,  the  process  under  these  conditions  proceeded  unin- 
terruptedly, pure  gypsum  first  crystallizing  out  from  the  liquid, 
and  subsequently,  the  hydrous  magnesian  carbonate,  f  This  ex- 
periment is  instructive  as  showing  the  results  which  must  have 
attended  this  process  in  past  ages,  when  the  quantity  of  carbonic 
acid  in  the  atmosphere  greatly  exceeded  its  present  amount. 

*  Amer.  Jour.  Sci.,  H,  xxxviii,  170,  365;  xlii,  49. 

t Proceedings  Royal  Institution,  May  30,  1867,  and  Canadian  Naturalist,  new  series, 
III,  231. 


58  ADDRESS    OF   T.    STERRY   HUNT. 

As  regards  the  hypotheses  put  forward  to  explain  the  supposed 
dolomitization  of  previously-formed  limestones  by  an  epigenic 
process,  I  may  remark  that  I  repeated  very  many  times,  under 
varying  conditions,  the  often  cited  experiment  of  Von  Morlot,  who 
claimed  to  have  generated  dolomite  by  the  action  of  sulphate  of 
magnesia  on  carbonate  of  lime,  in  the  presence  of  water  at  a  some- 
what elevated  temperature  under  pressure.  I  showed  that  what 
he  regarded  as  dolomite  was  not  such,  but  an  admixture  of  carbon- 
ate of  lime  with  anhydrous  and  sparingly  soluble  carbonate  of 
magnesia ;  the  conditions  in  which  the  carbonate  of  magnesia  is 
liberated  in  this  reaction,  not  being  favorable  to  its  union  with  the 
carbonate  of  lime  to  form  the  double  salt  which  constitutes  dolo- 
mite. The  experiment  of  Marignac,  who  thought  to  form  dolomite 
by  substituting  a  solution  of  chlorid  of  magnesium  for  the  sul- 
phate, I  found  to  yield  similar  results,  the  greater  part  of  the  mag- 
nesian  carbonate  produced  passing  at  once  into  the  insoluble 
condition,  without  combining  with  the  excess  of  carbonate  of  lime 
present.  The  process  for  the  production  of  the  double"  carbonate 
described  by  Ch.  Deville,  namely,  the  action  of  vapors  of  anhy- 
drous magnesian  chlorid  on  heated  carbonate  of  lime,  in  accord- 
ance with  Von  Buch's  strange  theory  of  dolomitization,  I  have  not 
thought  necessary  to  submit  to  the  test  of  experiment,  since  the 
conditions  required  are  scarcely  conceivable  in  nature.  Multiplied 
geognostical  observations  show  that  the  notion  of  the  epigenic 
production  of  dolomite  from  limestone  is  untenable,  although  its 
resolution  and  deposition  in  veins,  cavities,  or  pores  in  other  rocks 
is  a  phenomenon  of  frequent  occurrence. 

The  dolomites  or  magnesian  limestones  may  be  conveniently 
considered  in  two  classes  ;  first,  those  which  are  found  with  gyp- 
sums at  various  geological  horizons ;  and  second,  the  more  abun- 
dant and  widely  distributed  rocks  of  the  same  kind,  which  are  not 
associated  with  deposits  of  gypsum.  The  production  of  the  first 
class  is  dependent  upon  the  decomposition  of  sulphate  of  magne- 
sia by  solutions  of  bicarbonate  of  lime,  while  those  of  the  second 
class  owe  their  origin  to  the  decomposition  of  magnesian  chlorid 
or  sulphate  by  solutions  of  alkaline  bicarbonates.  In  both  cases, 
however,  the  bicarbonate  of  magnesia,  which  the  carbonated 
waters  generally  contain,  contributes  a  more  or  less  important 
part  to  the  generation  of  the  magnesian  sediments.  The  carbon- 
ated alkaline  waters  of  deep-seated  springs  often  contain,  as  is 


ORIGIN   OP  CRYSTALLINE  ROCKS.  59 

well  known,  besides  the  bicarbonates  of  soda,  lime,  and  magne- 
sia, compounds  of  iron,  manganese,  and  many  of  the  rarer  metals 
in  solution,  and  thus  the  metalliferous  character  of  many  of  the 
dolomites  of  the  second  class  is  explained.  The  simultaneous 
occurrence  of  alkaline  silicates  in  such  mineral  waters,  would 
give  rise,  as  already  pointed  out,  to  the  production  of  insoluble 
silicates  of  magnesia,  and  thus  the  frequent  association  of  such 
silicates  with  dolomites  and  magnesian  carbonates  in  the  crystal- 
line schists  is  explained,  as  marking  portions  of  one  continuous 
process.  The  formation  of  these  mineral  waters  depends  upon 
the  decomposition  of  feldspathic  rocks  by  subterranean  or  sub- 
aerial  processes,  which  were  doubtless  more  active  in  former  ages 
than  in  our  own.  The  subsequent  action  upon  magnesian  waters 
of  these  bicarbonated  solutions,  whether  alkaline  or  not,  is  de- 
pendent upon  climatic  conditions,  since,  in  a  region  where  the  rain- 
fall is  abundant,  such  waters  would  find  their  way  down  the  river- 
courses  to  the  open  sea,  where  the  excess  of  dissolved  sulphate  of 
lime  would  prevent  the  deposition  of  magnesian  carbonate.  It  is 
in  dry  and  desert  regions,  with  limited  lake-basins,  that  we  must 
seek  for  the  production  of  magnesian  carbonates,  and  I  have  ar- 
gued from  these  considerations  that  much  of  northeastern  Amer- 
ica, including  the  present  basins  of  the  Upper  Mississippi  and  St. 
Lawrence,  must,  during  long  intervals  in  the  paleozoic  period, 
have  had  a  climate  of  excessive  dryness,  and  a  surface  marked  by 
shallow  enclosed  basins,  as  is  shown  by  the  widely  spread  magne- 
sian limestones,  and  the  existence  of  gypsum  and  rock-salt  at 
more  than  one  geological  horizon  within  that  area.*  The  occur- 
rence of  serpentine  and  diallage  at  Syracuse,  New  York,  offers  a 
curious  example  of  the  local  development  of  crystalline  magne- 
sian silicates  in  Upper  Silurian  dolomitic  strata  under  conditions 
which  are  imperfectly  known,  and,  in  the  present  state  of  the 
locality,  cannot  be  studied.  | 

Since  the  uncombined  and  hydrated  magnesian  mono-carbonate 
is  at  once  decomposed  by  sulphate  or  chlorid  of  calcium,  it  fol- 
lows that  the  whole  of  these  lime-salts  in  a  sea-basin  must  be 
converted  into  carbonates  before  the  production  of  carbonated 
magnesian  sediments  can  begin.  The  carbonate  of  lime,  formed 

*  Geology  of  Southwestern  Ontario,  Amer.  Jour.  Sci.,  II,  xlvi,  355. 
t  Geology  of  the  3d  district  of  New  York,  108-110,  and  Hunt  on  Ophtolites,  Amer.  Jour. 
Sci.,  II,  xxvi,  236. 


60  ADDRESS    OF    T.    STERRY    HUNT. 

by  the  action  of  carbonates  of  magnesia  and  soda,  remains  at  first 
dissolved  as  bicarbonate,  and  is  only  separated  in  a  solid  form, 
when  in  excess,  or  when  required  for  the  needs  of  living  plants 
or  animals ;  which  are  dependent  for  their  supply  of  calcareous 
matter,  on  the  bicarbonate  of  lime  produced,  in  part  by  the  proc- 
ess just  described,  and  in  part  by  the  action  of  carbonic  acid  on 
insoluble  lime-compounds  of  the  earth's  solid  crust.  So  many 
limestones  are  made  up  of  calcareous  organic  remains,  that  a 
notion  exists  among  many  writers  on  geology  that  all  limestones 
are,  in  some  way,  of  organic  origin.  At  the  bottom  of  this  lies 
the  idea  of  an  analogy  between  the  chemical  relations  of  vege- 
table and  animal  life.  As  plants  give  rise  to  beds  of  coal,  so  ani- 
mals are  supposed  to  produce  limestones.  In  fact,  however,  the 
synthetic  process  by  which  the  growing  plant,  from  the  elements 
of  water,  carbonic  acid  and  ammonia,  generates  hydrocarbonace- 
ous  and  azotized  matters,  has  no  analogy  with  the  assimilative 
process  by  which  the  growing  animal  appropriates  alike  these  or- 
ganic matters  and  the  carbonate  and  phosphate  of  lime.  Without 
the  plant,  the  synthesis  of  the  hydrocarbons  would  not  take  place, 
while  independently  of  the  existence  of  coral  or  mollusk,  the  car- 
bonate of  lime  would  still  be  generated  by  chemical  reactions,  and 
would  accumulate  in  the  waters  until,  these  being  saturated,  its 
excess  would  be  deposited  as  gypsum  or  rock-salt  are  deposited. 
Hence  in  such  waters,  where,  from  any  causes,  life  is  excluded, 
accumulations  of  pure  carbonate  of  lime  maybe  formed.  In  1861 
I  called  attention  to  the  white  marbles  of  Vermont,  which  occur 
intercalated  among  impure  and  fossiliferous  beds,  as  apparently 
examples  of  such  a  process.* 

It  is  by  a  fallacy  similar  to  that  which  prevails  as  to  the  or- 
ganic origin  of  limestones,  that  Daubeny  and  Murchison  were  led 
to  appeal  to  the  absence  of  phosphates  from  certain  old  strata  as 
evidence  of  the  absence  of  organic  life  at  the  time  of  their  accu- 
mulation.! Phosphates,  like  silica  and  iron-oxyd,  were  doubtless 
constituents  of  the  primitive  earth's  crust,  and  the  production  of 
apatite  crystals  in  granitic  veins,  or  in  crystalline  schists,  is  a  proc- 
ess as  independent  of  life  as  the  formation  of  crystals  of  quartz 
or  of  hematite.  Growing  plants,  it  is  true,  take  up  from  the  soil 
or  the  waters  dissolved  phosphates,  which  pass  into  the  skeletons 

*  Amer.  Jour.  Sci.,  H,  xxxi,  402. 
t  Siluria,  4th  ed.,  pp.  28  and  537. 


ORIGIN   OF   CRYSTALLINE   ROCKS.  61 

of  animals,  a  process  which  has  been  active  from  very  remote  pe- 
riods. I  showed  in  1854  that  the  shells  of  Lingula  and  Orbicula, 
both  those  from  the  base  of  the  paleozoic  rocks  and  those  of  the 
present  time,  have  (like  Conularia  and  Serpulites)  a  chemical  com- 
position similar  to  the  skeletons  of  vertebrate  animals.*  The 
relations  of  both  carbonate  and  phosphate  of  lime  to  organized 
beings  are  similar  to  those  of  silica,  which,  like  them,  is  held  in 
watery  solution,  and  by  processes  independent  of  life  is  deposited 
both  in  amorphous  and  crystalline  forms,  but  in  certain  cases  is 
appropriated  by  diatoms  and  sponges,  and  made  to  assume  organ- 
ized shapes.  In  a  word,  the  assimilation  of  silica,  like  that  of 
phosphate  and  carbonate  of  lime,  is  a  purely  secondary  and  acci- 
dental process,  and  where  life  is  absent,  all  of  these  substances 
are  deposited  in  mineral  and  inorganic  forms. 


I  have  thus  endeavored  to  sketch,  in  a  concise  and  rapid  man- 
ner, the  history  of  the  earlier  rock-formations  of  eastern  North 
America,  and  of  our  progress  in  the  knowledge  of  them ;  while 
I  have,  at  the  same  time,  dwelt  upon  some  of  the  geognostical 
and  chemical  questions  which  their  study  suggests.  With  the 
record  of  the  last  thirty  years  before  them,  American  geologists 
have  cause  for  congratulation  that  their  investigations  have  been 
so  fruitful  in  great  results.  They  see,  however,  at  the  same  time, 
how  much  yet  remains  to  be  done  in  the  study  of  the  Appalachians 
and  of  our  northeastern  coast,  before  the  history  of  these  ancient 
rock-formations  can  be  satisfactorily  written.  Meanwhile  our  ad- 
venturous students  are  directing  their  labors  to  the  vast  regions  of 
western  America,  where  the  results  which  have  already  been  ob- 
tained are  of  profound  interest.  The  progress  of  these  investiga- 
tions will  doubtless  lead  us  to  modify  many  of  the  views  now 
accepted  in  science,  and  cannot  fail  greatly  to  enlarge  the  bound 
of  geological  knowledge. 

*  Amer.  Jour.  Sci.,  II,  xyii,  236. 


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